Organosiloxane compositions

ABSTRACT

A moisture curable composition capable of cure to an elastomeric body comprising
     (a) a diluted polymer comprising
       (i) a silicon containing polymer of the formula
 
X-A-X 1  
 
where X and X 1  are independently selected from silyl groups which contain one or more condensable substituents per group and A is a polymeric chain having a number average molecular weight (M n ) of at least 132 000; and a degree of polymerization of at least 1800.
   (ii) an organic extender and/or plasticizer
           which diluted polymer is obtained by polymerization in the presence of the said organic extender and/or plasticizer   
           
       (b) a suitable cross-linking agent which comprises at least two groups which are reactable with the condensable groups in the diluted polymer,   (c) a suitable condensation catalyst and optionally   (e) one or more fillers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/910,775, filed on May 20, 2008, now U.S. Pat. No. 7,754,800, whichclaims priority to and all the advantages of International PatentApplication No. PCT/US2006/011986, filed on Apr. 3, 2006, which claimspriority to Great Britain Patent Application Nos. GB 0506939.8 and GB0516239.1, filed on Apr. 6, 2005 and Aug. 6, 2005, respectively, all ofwhich are expressly incorporated herein by reference.

This invention is concerned with sealant compositions comprising highmolecular weight silicon containing polymers having condensable terminalgroups which have been polymerised in the presence of an extender and/orplasticiser.

The rheological properties of uncured polymers are primarily a functionof their viscosities. In general the lower the viscosity of a polymerthe higher the extrusion rate of uncured compositions which contain thepolymer. The viscosity of an uncured polymer is directly related to themolecular weight of the polymer and the length of the polymer chain,usually defined as the degree of polymerisation (dp). The viscosity ofthe uncured polymer is also a major influence on several of the physicalproperties of compositions incorporating the polymer such as, forexample, sealant compositions, when such compositions are subsequentlycured.

Organosiloxane compositions which cure to elastomeric solids are wellknown and such compositions can be produced to cure at either roomtemperature in the presence of moisture or with application of heat.Typically those compositions which cure at room temperature in thepresence of moisture are obtained by mixing a polydiorganosiloxane basedpolymer having reactive terminal groups, with a suitable silane (orsiloxane) based cross-linking agent in the presence of one or morefillers and a curing catalyst. These compositions are typically eitherprepared in the form of one-part compositions curable upon exposure toatmospheric moisture at room temperature or two part compositionscurable upon mixing at room temperature and pressure.

One important application of the above-described curable compositions istheir use as sealants. In use as a sealant, it is important that thecomposition has a blend of properties which render it capable of beingapplied as a paste to a joint between substrate surfaces where it can beworked, prior to curing, to provide a smooth surfaced mass which willremain in its allotted position until it has cured into an elastomericbody adherent to the adjacent substrate surfaces. Typically sealantcompositions are designed to cure quickly enough to provide a sound sealwithin several hours but at a speed enabling the applied material to betooled into a desired configuration shortly after application. Theresulting cured sealant is generally formulated to have a strength andelasticity appropriate for the particular joint concerned.

The introduction of an inorganic filler into an elastomeric compositioncontaining an organopolysiloxane containing polymer is often required toobtain useful tear, durometer, elongation and modulus at 100% elongationproperties. The rheological properties of an uncured elastomer aredependent on filler properties (when a filler is present in thecomposition) such as filler concentration and structure and the degreeof polymer-filler interaction as well as the viscosity of the polymer.In general the lower the viscosity of the uncured organopolysiloxanecontaining composition, optionally containing filler, the higher theextrusion rate of the uncured composition. As a result applicationsrequiring high extrusion rates such as uncured sealants, which in use,are generally extruded manually using a sealant gun or the like, need totypically be of relatively low viscosity (e.g. <100 000 mPa·s at 25° C.)to ensure suitable composition extrusion rates for manual end uses.

The physical properties of the resulting cured composition affectedinclude elongation and modulus at 100% elongation, both of which areparticularly important for sealants used in for example expansion jointsin the construction and transportation industries, where the need forsealants with low modulus and high elongation are essential.

Hence, whilst it is known that increasing the molecular weight of apolymer would improve some physical properties of a sealant typicallythe maximum viscosity used in current formulations are in practice nogreater than about 150 000 mPa·s at 25° C. Whilst polymers havingviscosities of up to 1,000,000 mPa·s at 25° C. have been discussed inthe prior art the use of polymers having such viscosities has beenpractically unmanageable. Hence, whilst it is known increasing themolecular weight of the polymer would improve the some properties of thesealant typically the maximum viscosity used in current formulations arein practice no greater than about 150 000 mPa·s at 25° C.

One method which has been used to increase the molecular weight of thepolymer whilst maintaining sufficiently low extrusion rates to enablethe composition to be manually extruded using e.g. sealant guns or thelike is the provision of chain extenders in the uncured composition. Thechain extender is mixed with a pre-prepared polymer and all the othercomposition ingredients and the composition is stored in an air tightmanner. Upon exposure to moisture the molecular weight of the polymer isincreased because the chosen chain extender is selected because it isknown to react at a faster rate with polymer terminal groups than thecross-linker provided in the composition. Examples of such methods aredescribed in U.S. Pat. No. 6,833,407, U.S. Pat. No. 4,020,044,US2004/0122199 and U.S. Pat. No. 5,300,612.

It has become common practice in the formulation of silicone basedcompositions used as room temperature cure sealants, to includeadditives which serve to “extend” and/or “plasticise” the siliconesealant composition by blending the or each extending compound(henceforth referred to as an “extender”) and/or plasticising compound(henceforth referred to as a “plasticiser”) with the pre-preparedpolymer and other ingredients of the composition.

An extender (sometimes also referred to as a process aid or secondaryplasticiser) is used to dilute the sealant composition and basicallymake the sealant more economically competitive without substantiallynegatively affecting the properties of the sealant formulation. Theintroduction of one or more extenders into a silicone sealantcomposition not only reduces the overall cost of the product but canalso affect the properties of resulting uncured and/or cured siliconesealants. The addition of extenders can, to a degree, positively effectthe rheology, adhesion and clarity properties of a silicone sealant andcan cause an increase in elongation at break and a reduction in hardnessof the cured product both of which can significantly enhance thelifetime of the cured sealant provided the extender is not lost from thecured sealant by, for example, evaporation or exudation.

A plasticiser (otherwise referred to as a primary plasticiser) is addedto a polymer composition to provide properties within the final polymerbased product to increase the flexibility and toughness of the finalpolymer composition. This is generally achieved by reduction of theglass transition temperature (T_(g)) of the cured polymer compositionthereby generally, in the case of sealants for example, enhancing theelasticity of the sealant which in turn enables movement capabilities ina joint formed by a silicone sealant with a significant decrease in thelikelihood of fracture of the bond formed between sealant and substratewhen a sealant is applied thereto and cured. Plasticisers are typicallyused to also reduce the modulus of the sealant formulation. Plasticisersmay reduce the overall unit cost of a sealant but that is not their mainintended use and indeed some plasticisers are expensive and couldincrease the unit cost of a sealant formulation in which they are used.Plasticisers tend to be generally less volatile than extenders and aretypically introduced into the polymer composition in the form of liquidsor low melting point solids (which become miscible liquids duringprocessing. Typically, for silicone based composition plasticisers areunreactive short chain siloxanes such as polydimethylsiloxane havingterminal triorganosiloxy groups wherein the organic substituents are,for example, methyl, vinyl or phenyl or combinations of these groups.Such polydimethylsiloxanes normally have a viscosity of from about 5 toabout 100,000 mPa·s. Compatible organic plasticisers may additionally beused, examples include dialkyl phthalates wherein the alkyl group may belinear and/or branched and contains from six to 20 carbon atoms such asdioctyl, dihexyl, dinonyl, didecyl, diallanyl and other phthalates;adipate, azelate, oleate and sebacate esters, polyols such as ethyleneglycol and its derivatives, organic phosphates such as tricresylphosphate and/or triphenyl phosphates, castor oil, tung oil, fatty acidsand/or esters of fatty acids.

Typically plasticisers are more compatible with polymer compositionsthan extenders and tend to be significantly less volatile and as suchare significantly more likely to remain at high levels within thepolymer matrix after curing.

Extenders need to be both sufficiently compatible with the remainder ofthe composition and as non-volatile as possible at the temperature atwhich the resulting cured sealant is to be maintained (e.g. roomtemperature). However it has been found that whilst some proposedextenders are effective during storage, at the time of application ofthe sealant and at least for a time thereafter, there are several wellknown problems regarding their use. These include:—

-   (i) UV stability—the discolouring of cured sealants containing    extenders upon prolonged exposure to UV light;-   (ii) Poor compatibility with the polymer composition (e.g. a sealant    composition) leading to their exuding from the sealant over time    which negatively effects the physical and aesthetic properties and    lifetime of the cured product e.g. sealant; and-   (iii) Staining of the surrounding substrates onto which the    extenders exude from the composition.

As previously mentioned the process used in the industry, forintroducing extenders and/or plasticisers into a polymer compositionsuch as a sealant composition, consists of merely mixing all thepre-prepared ingredients, e.g. polymer, cross-linker, catalyst, fillerand the or each extender and/or plasticiser together in appropriateamounts and orders of addition. Compatibility of organic extendersand/or plasticisers with the other ingredients in a silicone basedpolymer composition, is a significantly greater problem than withrespect to organic based polymers, silicone polymers into which theextenders and/or plasticisers are introduced tend to be highly viscouspolymers, and the chemical nature of the polymer being silicone based asopposed to organic based can have significant effects on thecompatibility. The level of compatibility effectively determines theamount of extender and/or plasticiser which can be introduced into apolymer composition. Typically this results in the introduction ofsignificantly lower amounts of, in particular, extenders into thecomposition than may be desired because the extender will not physicallymix into the polymer composition sufficiently well, particularly withthe pre-formed polymer which is usually the largest component, otherthan the filler, in the composition. The problem of compatibility ofplasticisers and extenders in silicone polymer compositions has been aknown in the industry ever since the introduction of organic extenders,which as far the inventors are aware, until the present invention hasnot been addressed other than by the proposal of an ever increasingnumber of organic based extenders.

DE3342026 describes a process involving the physical blending of aportion of pre-formed organosilicone polymer together with some or allof the plasticiser. The physical blending of polymer and plasticiser isexemplified in the examples using an alpha omegadihydroxypolydimethylsiloxane having a viscosity of merely about 80 000mPa·s at 20° C. thereby avoiding the problems which the presentinventors have addressed and which would be encountered using such aphysical blending process for high viscosity polymers wherein such ablending process would involve very expensive mixing equipment for longtime periods of time to obtain anything like a suitable blend renderingsuch a process economically unviable and most likely not provide asuitable blend.

Historically, unreactive siloxanes such as trialkylsilyl terminatedpolydiorganosiloxanes (for example trimethylsilyl terminatedpolydimethyl siloxane (PDMS)) were originally used as extenders and/orplasticisers in silicone based sealants because they were chemicallysimilar and had excellent compatibility.

A wide variety of organic compounds and compositions have been proposedfor use as extenders for reducing the cost of the silicone sealantcompositions. These materials are generally classified into two groupsas high volatility extenders and low volatility extenders.

Compositions containing high volatility extenders may contain e.g.toluene or xylene. The high volatility of these compounds causes anumber of disadvantages in sealant formulations including, highshrinkage (high volume loss due to evaporation of the solvent),flammability, VOC (volatile organic content), hazardous componentlabelling, health and safety issues, etc.

Low volatility extenders (sometimes referred to as higher molecularweight extenders), are chosen with the intention of having goodcompatibility with the polymers in the sealant compositions. Thesehigher molecular weight extenders can completely or partially replacethe PDMS plasticizer in the formulation.

Low molecular weight polyisobutylenes (PIB) are proposed as extenders inDE 2364856 and DE 3217516, however, due to the limited compatibility,the maximum amount of PIB extender that can be added to an acetoxysilicone sealant formulation is typically in the 25-30% (by weight)range. A higher addition level causes the extender to bleed to thesurface and makes the cured sealant surface sticky. Phosphate esters aredescribed as potential extenders in DE 2802170 and DE 2653499.

Mineral oil fractions (e.g. isoparaffins) and polyalkylbenzenes such asheavy alkylates (alkylated aromatic materials remaining afterdistillation of oil in a refinery) have also been proposed as extenders.These and other organic compounds and mixtures proposed as extendermaterials for silicone sealant compositions are described in thefollowing publications:—

GB2041955 describes the use of dodecyl benzene and other alkylarenes asorganic extenders. GB2012789 describes the use of trioctyl phosphate forthe partial replacement of PDMS. DE3342026 and DE3342027 describe theuse of esters of aliphatic monocarboxylic acids as extenders. EP0043501proposes the use of between 0.2 and 15% by weight of the sealantcomposition of branched and/or cyclic paraffin hydrocarbons such ascyclohexane, isohexane and isooctodecane. EP0801101 describes the use ofa mixture of paraffin oils (molecular weight>180) in combination withone or more alkyl aromatic compounds. EP0842974 describes the use ofalkylcyclohexanes (molecular weight>220). WO99/66012 and WO 00/27910describe oil resistant silicone compositions containing one or morealiphatic liquid polymers and oils, petroleum derived organic oils,alkyl phosphates, polyalkylene glycol, poly (propylene oxides),hydroxyethylated alkyl phenol, dialkyldithiophosphonate, poly(isobutylenes), poly (a-olefins) and mixtures thereof as extenders.

In recent years the industry has increasingly used paraffinichydrocarbons as extenders. EP0885921 describes the use of paraffinichydrocarbon mixtures containing 60 to 80% paraffinic and 20 to 40%naphthenic and a maximum of 1% aromatic carbon atoms. EP 0807667 appearsto describe a similar extender comprising wholly or partially of aparaffin oil comprising 36-40% cyclic paraffin oils and 58 to 64%non-cyclic paraffin oils. WO99/65979 describes an oil resistant sealantcomposition comprising a plasticiser which may include paraffinic ornaphthenic oils and mixtures thereof amongst other plasticisers.EP1481038 describes the use of a hydrocarbon fluid containing more than60 wt. % naphthenics, at least 20 wt. % polycyclic naphthenics and anASTM D-86 boiling point of from 235 to 400° C. EP1252252 describes theuse of an extender comprising a hydrocarbon fluid having greater than 40parts by weight cyclic paraffinic hydrocarbons and less than 60 parts byweight monocyclic paraffinic hydrocarbons based on 100 parts by weightof hydrocarbons. EP1368426 describes a sealant composition for use withalkyd paints containing a liquid paraffinic hydrocarbon “extender” whichpreferably contains greater than 40% by weight of cyclic paraffins.

As mentioned above a fundamental problem with the use of extendingmaterials is their lack of compatibility with components in the uncuredsilicone sealant composition typically resulting in phase separationduring storage and exudation from the cured sealant over the completetemperature range of interest. It is commonly found that, after curing,extended sealants exude extender resulting in a significant reduction inthe lifetime of the cured sealant, a feature particularly prevalent withextenders having low boiling points, e.g. <100° C. Whilst it is in theinterest of the manufacturer to incorporate a high loading of extenderinto their sealant compositions, the physical mixing of the extendermaterial with the other ingredients as advocated in all of the abovedocuments is prevented through the lack of compatibility particularlywith respect to high viscosity polymers where the viscous properties ofthe polymer component are a physical barrier to the incorporation oflarge volumes of extender into the sealant compositions. It is generallyfound therefore that the amount of extender, which may be incorporatedinto the sealant composition, is typically between 20 and 40% by weightdependent on the extender or combination of extenders used.

Whilst many of the organic extenders proposed above have potential theyall generally have problems for example whilst alkylbenzene extendershave a seemingly suitable combination of properties, i.e. high boilingpoints, excellent compatibility with the polydiorganosiloxane polymermatrix (resulting in cured silicone sealants of good to excellenttransparency), low environmental impact, low vapour pressure (andtherefore low shrinkage), positive effect on the rheological properties(reduced stringing). However, when exposed to artificial or naturalweathering, alkyl benzene extended sealants tend to yellow ratherrapidly. After prolonged weathering, these extended sealants continue toyellow, and also lose their transparency. This problem does not occurwith other extenders, such as phosphate esters or polyisobutylene.

Furthermore, whilst the use of polymers with very high degrees ofpolymerisation in siloxane formulations, can result in severaladvantageous properties such as high elasticity the viscosity of suchpolymers is generally so great (i.e. silicone gums) that they becomeeither completely unmanageable with respect to inter-mixing with otheringredients, such as fillers, cross-linkers, extenders and/orplasticisers, or require very high shear mixers which are expensive tooperate and would be almost certain to fail to provide an evendispersion of the composition constituents (particularly filler andextender and/or plasticiser) in the polymer. There has therefore been along-felt need within the industry to develop a process for the ease ofintroduction of silicone based polymers of very high degrees ofpolymerisation into compositions whilst avoiding the need for high costequipment.

In accordance with the present invention there is provided a moisturecurable composition capable of cure to an elastomeric body comprising

-   (a) a diluted polymer comprising    -   (i) a silicon containing polymer of the formula        X-A-X¹    -   where X and X¹ are independently selected from silyl groups        which contain one or more condensable substituents per group and        A is a polymeric chain having a number average molecular weight        (M_(n)) of at least 132 000; and a degree of polymerisation of        at least 1800.    -   (ii) an organic extender and/or plasticiser    -   which diluted polymer is obtained by polymerisation in the        presence of the said organic extender and/or plasticiser-   (b) a suitable cross-linking agent which comprises at least two    groups which are reactable with the condensable groups in the    diluted polymer,-   (c) a suitable condensation catalyst and optionally-   (e) one or more fillers.

The concept of “comprising” where used herein is used in its widestsense to mean and to encompass the notions of “include” and “consistof”.

For the sake of clarification, the term “monomer” and derivativesthereof are used herein to mean a monomer or oligomer starting materialinvolved in a polymerisation process.

Preferably each extender and or plasticiser is miscible or at leastsubstantially miscible with the monomeric starting materials with whichthey are initially mixed, and more particularly with both intermediatepolymerisation reaction products and the final polymerisation product.The term “Substantially miscible extenders and/or plasticisers” areintended to include extenders and/or plasticisers which are completelyor largely miscible with the monomer(s) and/or the reaction mixtureduring polymerisation and hence may include low melting point solidswhich become miscible liquids in a reaction mixture during thepolymerisation process.

An organosiloxane containing polymer is intended to mean a polymercomprising multiple organopolysiloxane groups per molecule and isintended to include a polymer substantially containing onlyorganopolysiloxane groups in the polymer chain or polymers where thebackbone contains both organopolysiloxane groups and e.g. organicpolymeric groups in chain.

The diluted polymer comprises a polymer component which in accordancewith the present invention is a silicon containing polymer having anumber average molecular weight (M_(n)) of at least 132 000 asdetermined following ASTM D5296-05 and calculated as polystyrenemolecular weight equivalents and a degree of polymerisation of at least1800. For organopolysiloxane polymers an M_(n) value of 132 000 equateto a weight averaged molecular weight (M_(w)) of 198,000. and wouldtypically have a viscosity of greater than 1000000 mPa·s at 25° C.

Preferably the silicon containing polymer is an organosiloxanecontaining polymer preferably having the following general formulaX¹-A-X²  (1)where X¹ and X² suitable silicon containing condensable groups and A isa siloxane polymeric chain, an organic polymeric chain, a siloxanecopolymeric chain or a siloxane/organic block copolymeric chain.Each X¹ or X² group contains a suitable condensable substituent which ischosen to react with the chosen cross-linker via a condensationreaction. For the avoidance of doubt condensation is a reaction betweenreactants which result in the elimination of low molecular weightby-product(s) such as water, ammonia or methanol etc.The sort of reaction envisaged between the condensable end groups of thepolymer and the cross-linker are most preferably generally linked to theinteraction of compounds having hydroxyl and/or hydrolysable end groupswhich can interact with the release of e.g. water or methanol or thelike. However, the following list indicates other interactions whichmight be considered for the cure process of the composition inaccordance with the present invention:—

-   1) the condensation of organohalosilyl groups with an    organoalkoxysilyl groups,-   2) the condensation of organohalosilyl groups with    organoacyloxysilyl groups,-   3) the condensation of organohalosilyl groups with organosilanols,-   4) the condensation of organohalosilyl groups with silanolates,-   5) the condensation of organo-hydrosilyl groups with organosilanol    groups-   6) the condensation of organoalkoxysilyl groups with    organoacyloxysilyl groups-   7) the condensation of organoalkoxysilyl groups with organosilanol    groups,-   8) the condensation of organoaminosilyl groups with organosilanols,-   9) the condensation of organoacyloxysilyl groups silanolate groups-   10) the condensation of organoacyloxysilyl groups with    organosilanols,-   11) the condensation of organooximosilyl groups with organosilanol    groups-   12) the condensation of organoenoxysilyl groups with organosilanols,-   13) The condensation of a siloxane compound comprising one or more    hydrosilane functional groups with a siloxane compounds containing    at least one alkoxysilane functional group, generating hydrocarbon    by-products.    However preferably X¹ or X² are silyl groups comprising    hydroxyl-terminating or hydrolysable substituents such as —SiOH₃,    —(R^(a))SiOH₂, —(R^(a))₂SiOH, —R^(a)Si(OR^(b))₂, —Si(OR^(b))₃,    —R^(a) ₂SiOR^(b) or    —R^(a) ₂ Si—R^(c)—SiR^(d) _(p)(OR^(b))_(3−p) where each R^(a)    independently represents a monovalent hydrocarbyl group, for    example, an alkyl group, in particular having from 1 to 8 carbon    atoms, (and is preferably methyl); each R^(b) and R^(d) group is    independently an alkyl or alkoxy group in which the alkyl groups    suitably have up to 6 carbon atoms; R^(c) is a divalent hydrocarbon    group which may be interrupted by one or more siloxane spacers    having up to six silicon atoms; and p has the value 0, 1 or 2.    Suitably, X¹ and/or X² are groups which are hydrolysable in the    presence of moisture.    In one embodiment a proportion (up to 20%) of X² groups may be    trialkylsilyl groups.

Examples of suitable siloxane containing polymeric chain A in formula(I) are those which comprise a polydiorgano-siloxane chain. Thus group Apreferably includes siloxane units of formula (2)—(R⁵ _(s)SiO_((4−s)/2))—  (2)in which each R⁵ is independently an organic group such as a hydrocarbongroup having from 1 to 18 carbon atoms, a substituted hydrocarbon grouphaving from 1 to 18 carbon atoms or a hydrocarbonoxy group having up to18 carbon atoms and a has, on average, a value of from 1 to 3,preferably 1.8 to 2.2. Preferably R⁵ is a hydrocarbyl group having from1 to 10 carbon atoms optionally substituted with one or more halogengroup such as chlorine or fluorine and s is 0, 1 or 2. Particularexamples of groups R⁵ include methyl, ethyl, propyl, butyl, vinyl,cyclohexyl, phenyl, tolyl group, a propyl group substituted withchlorine or fluorine such as 3,3,3-trifluoropropyl, chlorophenyl,beta-(perfluorobutyl)ethyl or chlorocyclohexyl group. Suitably, at leastsome and preferably substantially all of the groups R⁵ are methyl.

Polymeric chain A in the compound of formula (1) may include anysuitable siloxane or siloxane/organic molecular chain providing theresulting polymer a viscosity (in the absence of diluents in accordancewith the present invention of up to at least 20 000 000 mPa·s, at 25° C.(i.e. a degree of polymerisation (dp) of up to or even more than 200 000units of formula (2)). In one preferred embodiment polymeric chain A isa linear organopolysiloxane molecular chain (i.e. s=2) for all chainunits. Preferred materials have polydiorganosiloxane chains according tothe general formula (3)—(R⁵ ₂SiO)_(t)—  (3)in which each R⁵ is as defined above and is preferably a methyl groupand t has a value of up to 200 000. Suitable polymers have viscositiesof up to at least 20 000 000 mPa·s at 25° C. in the absence of theextender(s) but when prepared in the presence of the extender(s)viscosities are generally in the order of 1000 to 100 000 mPa·s at 25°C. because of the presence of the extender(s) in the polymer matrix. Thepolydiorganosiloxanes may be homopolymers or copolymers. Mixtures ofdifferent polydiorganosiloxanes having terminal condensable groups arealso suitable.

Whilst polymeric chain A is preferably exclusively an organopolysiloxanechain, polymeric chain A may alternatively be a block copolymeric chaincomprising at least one block of siloxane groups of the type depicted informula (2) above and an organic component comprising any suitableorganic based polymer backbone for example the organic polymer backbonemay comprise, for example, polystyrene and/or substituted polystyrenessuch as poly(α-methylstyrene), poly(vinylmethylstyrene),poly(p-trimethylsilylstyrene) andpoly(p-trimethylsilyl-α-methylstyrene). Other organic components whichmay be incorporated in the polymeric chain A may include acetyleneterminated oligophenylenes, vinylbenzyl terminated aromaticpolysulphones oligomers, aromatic polyesters, aromatic polyester basedmonomers, polyalkylenes, polyurethanes, aliphatic polyesters, aliphaticpolyamides and aromatic polyamides and the like.

However perhaps the most preferred organic based polymeric blocks in Aare polyoxyalkylene based blocks. Such polyoxyalkylene blocks preferablycomprise a linear predominantly oxyalkylene polymer comprised ofrecurring oxyalkylene units, (—C_(n)H_(2n)—O—) illustrated by theaverage formula (—C_(n)H_(2n)—O—)_(y) wherein n is an integer from 2 to4 inclusive and y is an integer of at least four. The number averagemolecular weight of each polyoxyalkylene polymer block may range fromabout 300 to about 10,000. Moreover, the oxyalkylene units are notnecessarily identical throughout the polyoxyalkylene monomer, but candiffer from unit to unit. A polyoxyalkylene block, for example, can becomprised of oxyethylene units, (—C₂H₄—O—); oxypropylene units(—C₃H₆—O—); or oxybutylene units, (—C₄H₈—O—); or mixtures thereof.

Other polyoxyalkylene blocks may include, for example, units of thestructure——[—R^(e)—O—(—R^(f)—O—)_(p)-Pn-CR^(g) ₂-Pn-O—(—R^(f)—O—)_(q)—R^(e)]—in which Pn is a 1,4-phenylene group, each R^(e) is the same ordifferent and is a divalent hydrocarbon group having 2 to 8 carbonatoms, each R^(f) is the same or different and, is, an ethylene group orpropylene group, each R^(g) is the same or different and is, a hydrogenatom or methyl group and each of the subscripts p and q is a positiveinteger in the range from 3 to 30. Alternatively A may solely comprisean organic based polymeric chain in which case A may comprise any of theorganic polymeric chains discussed above in respect to block copolymers.

Any suitable extenders or combination of extenders may be utilised asthe extender in the extended polymer.

These include each of the following alone or in combination with othersfrom the list:—trialkylsilyl terminated polydialkyl siloxane where thealkyl groups are preferably methyl groups;

polyisobutylenes (PIB),

phosphate esters such as trioctyl phosphate

polyalkylbenzenes,

linear and/or branched alkylbenzenes such as heavy alkylates, dodecylbenzene and other alkylarenes,

esters of aliphatic monocarboxylic acids;

unreactive short chain siloxanes

linear or branched mono unsaturated hydrocarbons such as linear orbranched alkenes or mixtures thereof containing from 12 to 25 carbonatoms; and/or mineral oil fractions comprising linear (e.g.n-paraffinic) mineral oils, branched (iso-paraffinic) mineral oils,cyclic (referred in some prior art as naphthenic) mineral oils andmixtures thereof. Preferably the hydrocarbons utilised comprise from 5to 25 carbon atoms per molecule.

Preferred extenders include the mineral oil fractions,alkylcycloaliphatic compounds, and alkybenzenes includingpolyalkylbenzenes.

Other preferred mineral oil extenders include alkylcycloaliphaticcompounds and alkybenzenes including polyalkylbenzenes.

Any suitable mixture of mineral oil fractions may be utilised as theextender in the present invention but high molecular weight extenders(e.g. a number average molecular weight>220) are particularly preferred.Examples include:—

alkylcyclohexanes (having a number average molecular weight>220);

paraffinic hydrocarbons and mixtures thereof containing from 1 to 99%,preferably from 15 to 80% n-paraffinic and/or isoparaffinic hydrocarbons(linear branched paraffinic) and 1 to 99%, preferably 85 to 20% cyclichydrocarbons (naphthenic) and a maximum of 3%, preferably a maximum of1% aromatic carbon atoms. The cyclic paraffinic hydrocarbons(naphthenics) may contain cyclic and/or polycyclic hydrocarbons. Anysuitable mixture of mineral oil fractions may be used, e.g. mixturescontaining

-   -   (i) 60 to 80% paraffinic and 20 to 40% naphthenic and a maximum        of 1% aromatic carbon atoms;    -   (ii) 30-50%, preferably 35 to 45% naphthenic and 70 to 50%        paraffinic and or isoparaffinic oils;    -   (iii) hydrocarbon fluids containing more than 60 wt. %        naphthenics, at least 20 wt. % polycyclic naphthenics and an        ASTM D-86 boiling point of greater than 235° C.;    -   (iv) hydrocarbon fluid having greater than 40 parts by weight        naphthenic hydrocarbons and less than 60 parts by weight        paraffinic and/or ispoaraffinic hydrocarbons based on 100 parts        by weight of hydrocarbons.

Preferably the mineral oil based extender or mixture thereof comprisesat least one of the following parameters:—

-   -   (i) a molecular weight of greater than 150, most preferably        greater than 200;    -   (ii) an initial boiling point equal to or greater than 230° C.        (according to ASTM D 86).    -   (iii) a viscosity density constant value of less than or equal        to 0.9; (according to ASTM 2501)    -   (iv) an average of at least 12 carbon atoms per molecule, most        preferably 12 to 30 carbon atoms per molecule;    -   (v) an aniline point equal to or greater than 70° C., most        preferably the aniline point is from 80 to 110° C. (according to        ASTM D 611);    -   (vi) a naphthenic content of from 20 to 70% by weight of the        extender and a mineral oil based extender has a paraffinic        content of from 30 to 80% by weight of the extender according to        ASTM D 3238);    -   (vii) a pour point of from −50 to 60° C. (according to ASTM D        97);    -   (viii) a kinematic viscosity of from 1 to 20 cSt at 40° C.        (according to ASTM D 445)    -   (ix) a specific gravity of from 0.7 to 1.1 (according to ASTM        D1298);    -   (x) a refractive index of from 1.1 to 1.8 at 20° C. (according        to ASTM D 1218)    -   (xi) a density at 15° C. of greater than 700 kg/m³ (according to        ASTM D4052) and/or    -   (xii) a flash point of greater than 100° C., more preferably        greater than 110° C. (according to ASTM D 93)    -   (xiii) a saybolt colour of at least +30 (according to ASTM D        156)    -   (xiv) a water content of less than or equal to 250 ppm        (according to ASTM D6304)    -   (xv) a Sulphur content of less than 2.5 ppm (according to ASTM D        4927)

The alkylbenzene compounds suitable for use include heavy alkylatealkylbenzene or an alkylcycloaliphatic compound. Examples of alkylsubstituted aryl compounds useful as extenders and/or plasticisers arecompounds which have aryl groups, especially benzene substituted byalkyl and possibly other substituents, and a molecular weight of atleast 200. Examples of such extenders are described in U.S. Pat. No.4,312,801, the content of which is incorporated herein by reference.These compounds can be represented by general formula (I), (II), (III)and (IV)

where R⁶ is an alkyl chain of from 1 to 30 carbon atoms, each of R⁷through to R¹⁶ is independently selected from hydrogen, alkyl, alkenyl,alkynyl, halogen, haloalkyl, nitrile, amine, amide, an ether such as analkyl ether or an ester such as an alkyl ester group, and n is aninteger of from 1 to 25.

In particular, the extender used in accordance with the process of thepresent invention is of formula (1) where each of R⁷, R⁸, R⁹, R¹⁰ andR¹¹ is hydrogen and R⁶ is a C₁₀-C₁₃ alkyl group. A particularly usefulsource of such compounds are the so-called “heavy alkylates”, which arerecoverable from oil refineries after oil distillation. Generallydistillation takes place at temperatures in the range of from 230-330°C., and the heavy alkylates are present in the fraction remaining afterthe lighter fractions have been distilled off.

Examples of alkylcycloaliphatic compounds are substituted cyclohexaneswith a molecular weight in excess of 220. Examples of such compounds aredescribed in EP 0842974, the content of which is incorporated herein byreference. Such compounds may be represented by general formula (V).

where R¹⁷ is a straight or branched alkyl group of from 1 to 25 carbonatoms, and R¹⁸ and R¹⁹ are independently selected from hydrogen or aC₁₋₂₅ straight or branched chain alkyl group.

The amount of diluent which may be included in the composition willdepend upon factors such as the purpose to which the composition is tobe put, the molecular weight of the diluent(s) concerned etc. Polymerproducts in accordance with the present invention may contain from 5%w/w up to 70% w/w diluent (based on the combined weight of polymer anddiluent(s)) depending upon these factors. In general however, the higherthe molecular weight of the diluent(s), the less will be tolerated inthe composition. Typical compositions will contain up to 70% w/wdiluent(s). More suitable polymer products comprise from 30-60% w/w of alinear diluent(s) whereas 25-35% w/w will be more preferred when thediluent is a heavy alkylate.

Most preferably the extender comprises a mineral oil fraction.

Any suitable cross-linker may be used provided it is able to participatein condensation reaction with the polymer. The cross-linker (b) used inthe moisture curable composition as hereinbefore described is preferablya silane or siloxane compound containing at least two and preferably atleast 3 hydroxyl and/or hydrolysable groups. These include one or moresilanes or siloxanes which contain silicon bonded hydrolysable groupssuch as acyloxy groups (for example, acetoxy, octanoyloxy, andbenzoyloxy groups); ketoximino groups (for example dimethyl ketoximo,and isobutylketoximino); alkoxy groups (for example methoxy, ethoxy, anpropoxy) and alkenyloxy groups (for example isopropenyloxy and1-ethyl-2-methylvinyloxy).

In the case of siloxane based cross-linkers the molecular structure canbe straight chained, branched, or cyclic.

The cross-linker may have two but preferably has three or foursilicon-bonded condensable (preferably hydrolysable) groups permolecule. When the cross-linker is a silane and when the silane hasthree silicon-bonded hydrolysable groups per molecule, the fourth groupis suitably a non-hydrolysable silicon-bonded organic group. Thesesilicon-bonded organic groups are suitably hydrocarbyl groups which areoptionally substituted by halogen such as fluorine and chlorine.Examples of such fourth groups include alkyl groups (for example methyl,ethyl, propyl, and butyl); cycloalkyl groups (for example cyclopentyland cyclohexyl); alkenyl groups (for example vinyl and allyl); arylgroups (for example phenyl, and tolyl); aralkyl groups (for example2-phenylethyl) and groups obtained by replacing all or part of thehydrogen in the preceding organic groups with halogen. Preferablyhowever, the fourth silicon-bonded organic groups is methyl.

Silanes and siloxanes which can be used as cross-linkers includealkyltrialkoxysilanes such as methyltrimethoxysilane (MTM) andmethyltriethoxysilane, alkenyltrialkoxy silanes such asvinyltrimethoxysilane and vinyltriethoxysilane, isobutyltrimethoxysilane(iBTM). Other suitable silanes include ethyltrimethoxysilane,vinyltriethoxysilane, phenyltrimethoxysilane, alkoxytrioximosilane,alkenyltrioximosilane, 3,3,3-trifluoropropyltrimethoxysilane,methyltriacetoxysilane, vinyltriacetoxysilane, ethyl triacetoxysilane,di-butoxy diacetoxysilane, phenyl-tripropionoxysilane,methyltris(methylethylketoximo)silane,vinyl-tris-methylethylketoximo)silane,methyltris(methylethylketoximino)silane, methyltris(isopropenoxy)silane,vinyltris(isopropenoxy)silane, ethylpolysilicate, n-propylorthosilicate,ethylorthosilicate, dimethyltetraacetoxydisiloxane. The cross-linkerused may also comprise any combination of two or more of the above.

The amount of cross-linker present in the composition will depend uponthe particular nature of the cross-linker and in particular, themolecular weight of the molecule selected. The compositions suitablycontain cross-linker in at least a stoichiometric amount as compared tothe polymeric material described above. Compositions may contain, forexample, from 2-30% w/w of cross-linker, but generally from 2 to 10%w/w. Acetoxy cross-linkers may typically be present in amounts of from 3to 8% w/w preferably 4 to 6% w/w whilst oximino cross-linkers, whichhave generally higher molecular weights will typically comprise from3-8% w/w.

The composition further comprises a condensation catalyst. The catalystchosen for inclusion in a particular silicone sealant compositiondepends upon the speed of cure required. Any suitable condensationcatalyst may be utilised to cure the composition including tin, lead,antimony, iron, cadmium, barium, manganese, zinc, chromium, cobalt,nickel, titanium, aluminium, gallium or germanium and zirconium basedcatalysts such as organic tin metal catalysts and 2-ethylhexoates ofiron, cobalt, manganese, lead and zinc may alternatively be used.Organotin, titanate and/or zirconate based catalysts are preferred.

Silicone sealant compositions which contain oximosilanes oracetoxysilanes generally use a tin catalyst for curing, such astriethyltin tartrate, tin octoate, tin oleate, tin naphthate,butyltintri-2-ethylhexoate, tinbutyrate, carbomethoxyphenyl tintrisuberate, isobutyltintriceroate, and diorganotin salts especiallydiorganotin dicarboxylate compounds such as dibutyltin dilaurate,dimethyltin dibutyrate, dibutyltin dimethoxide, dibutyltin diacetate,dimethyltin bisneodecanoate Dibutyltin dibenzoate, stannous octoate,dimethyltin dineodeconoate, dibutyltin dioctoate. Dibutyltin dilaurate,dibutyltin diacetate are particularly preferred.

For compositions which include alkoxysilane cross-linker compounds, thepreferred curing catalysts are titanate or zirconate compounds. Suchtitanates may comprise a compound according to the general formulaTi[OR²²]₄ where each R²² may be the same or different and represents amonovalent, primary, secondary or tertiary aliphatic hydrocarbon groupwhich may be linear or branched containing from 1 to 10 carbon atoms.Optionally the titanate may contain partially unsaturated groups.However, preferred examples of R²² include but are not restricted tomethyl, ethyl, propyl, isopropyl, butyl, tertiary butyl and a branchedsecondary alkyl group such as 2,4-dimethyl-3-pentyl. Preferably, wheneach R²² is the same, R²² is an isopropyl, branched secondary alkylgroup or a tertiary alkyl group, in particular, tertiary butyl. Examplesinclude tetrabutyltitanate, tetraisopropyltitanate, or chelatedtitanates or zirconates such as for example diisopropylbis(acetylacetonyl)titanate, diisopropylbis(ethylacetoacetonyl)titanate, diisopropoxytitaniumBis(Ethylacetoacetate) and the like. Further examples of suitablecatalysts are described in EP1254192 which is incorporated herein byreference. The amount of catalyst used depends on the cure system beingused but typically is from 0.01 to 3% by weight of the total composition

Alternatively, the titanate may be chelated. The chelation may be withany suitable chelating agent such as an alkyl acetylacetonate such asmethyl or ethylacetylacetonate. The catalyst may therefore comprise amixture or reaction product of

-   -   (i) M(OR)₄ or (ii) M(OR′)_(x)(Z)_(z)        wherein M is titanium or zirconium, each R′ is the same or        different and is a primary, secondary or tertiary aliphatic        carbon groups or —SiR⁹ ₃, in which each R⁹ is an alkyl group        having from 1 to 6 carbon atoms;        Z is a group of the formula —O—Y—O— wherein Y is an optionally        branched alkylene group comprising from 1 to 8 carbon atoms; and        x is 0 or 2, wherein when x is 0, z is 2 and when x is 2, z is        1;        with        (iii) a compound having the general formula:

In whichR¹ is an optionally substituted alkylene radical having from 1 to 6carbon atoms,A′ is selected from the group consisting of:(!)—(CX₂)_(n)C(R²)₃ wherein n is from 0 to 5,(!!) an adamantyl group and(!!!) an adamantyl derivative;B′ is selected from the group consisting of:a″)—(CX₂)_(t)C(R²)₃, wherein t has a value of from 0 to 5,b″) a monovalent alkyl group having from 1 to 6 carbon atoms, andc″) OR³, wherein R³ is selected from (a″) or (b″)each X is the same or different and is a halogen group or hydrogen;each R² is the same or different and is X or an alkyl radical having oneto eight carbon atoms

These materials are produced, for example, by reacting an alcoholate asreferred to above with an α- or β-diketone or a derivative thereof. Morepreferred are those partially chelated titanium compounds having twoalcoholate groups attached to titanium. The most preferredorganotitanium compounds are those wherein the two alcoholate groups arecomposed of more than 3 carbon atoms, for example, bis(diethyleneglycoxy)-titanium-(2,4-pentanedionate).

When Z is —O—Y—O— each oxygen atom is bound directly to the titaniumatom and x is about 2. Preferably Y is an alkylene group containing 1 to8 carbon atoms. Examples of the O—Y—O group may include 1,3-dioxypropane(O—(CH₂)₃—O), 2,4-dimethyl-2,4-dioxypentane(O—C((CH₃)₂)—CH₂—C((CH₃)₂)—O) and 2,3-dimethyl-2,3-dioxybutane(O—C((CH₃)₂)—C—((CH₃)₂)—O)

Regarding now compound (iii), preferably at least one and mostpreferably each X is a halogen radical. Most preferably the halogenradical is a fluorine radical. Similarly it is preferred that at leastone and most preferably each R² group is a halogen radical and mostpreferably it is a fluorine radical or each R² group is an alkyl group,most preferably a methyl or ethyl or butyl group. In a most preferredformulation n is zero. R¹ is most preferably a methylene group but canhave one alkyl or halogen substituted alkyl group with 1 to 5 carbonatoms. The adamantyl group is a derivative of adamantane ortricyclo-3,3,1,1-decane which is a rigid ring system based on threefused cyclohexane rings.

Examples of compound (iii) include Methyl pivaloylacetate (MPA) andEthyl 4,4,4-trifluoroacetoacetate (TFA)

Preferably the catalyst, component (c), will be present in an amount offrom 0.3 to 6 parts by weight per 100 parts by weight of component (a),i.e. from about 0.2 to 2 weight % of the composition component (c) maybe present in an amount of greater than 6 parts by weight in cases wherechelating agents are used.

In one embodiment the process is used to prepare a one or two partorganopolysiloxane sealant composition. A two part composition comprisesin the first part diluted polymer and filler (when required) and in thesecond part catalyst and cross-linker are provided for mixing in anappropriate ratio (e.g. from 1:1 to 10:1) immediately prior to use.Additional additives to be discussed below may be provided in eitherpart 1 or part 2 of the part composition but are preferably added inpart two.

The one or two part compositions of the present invention may beformulated as to be stable in storage but cure on exposure toatmospheric moisture (after mixing in the case of two part compositions)and may be employed in a variety of applications, for example ascoating, caulking and encapsulating materials. They are, however,particularly suitable for sealing joints, cavities and other spaces inarticles and structures which are subject to relative movement. They arethus particularly suitable as glazing sealants and for sealing buildingstructures where the visual appearance of the sealant is important.

Thus in a further aspect, the invention provides a method of sealing aspace between two units, said method comprising applying a compositionas described above and causing or allowing the composition to cure.Suitable units include glazing structures or building units as describedabove and these form a further aspect of the invention.

Compositions of this invention may contain, as optional constituents,other ingredients which are conventional to the formulation of siliconerubber sealants and the like. For example, the compositions willnormally contain one or more finely divided, reinforcing fillers such ashigh surface area fumed and precipitated silicas and to a degree calciumcarbonate as discussed above, or additional non-reinforcing fillers suchas crushed quartz, diatomaceous earths, barium sulphate, iron oxide,titanium dioxide and carbon black, talc, wollastonite. Other fillerswhich might be used alone or in addition to the above include aluminite,calcium sulphate (anhydrite), gypsum, calcium sulphate, magnesiumcarbonate, clays such as kaolin, aluminium trihydroxide, magnesiumhydroxide (brucite), graphite, copper carbonate, e.g. malachite, nickelcarbonate, e.g. zarachite, barium carbonate, e.g. witherite and/orstrontium carbonate e.g. strontianite

Aluminium oxide, silicates from the group consisting of olivine group;garnet group; aluminosilicates; ring silicates; chain silicates; andsheet silicates. The olivine group comprises silicate minerals, such asbut not limited to, forsterite and Mg₂SiO₄. The garnet group comprisesground silicate minerals, such as but not limited to, pyrope;Mg₃Al₂Si₃O₁₂; grossular; and Ca₂Al₂Si₃O₁₂. Aluninosilicates compriseground silicate minerals, such as but not limited to, sillimanite;Al₂SiO₅; mullite; 3Al₂O₃.2SiO₂; kyanite; and Al₂SiO₅

The ring silicates group comprises silicate minerals, such as but notlimited to, cordierite and Al₃(Mg,Fe)₂[Si₄AlO₁₈]. The chain silicatesgroup comprises ground silicate minerals, such as but not limited to,wollastonite and Ca[SiO₃].

The sheet silicates group comprises silicate minerals, such as but notlimited to, mica; K₂AI₁₄[Si₆Al₂O₂₀](OH)₄; pyrophyllite;Al₄[Si₈O₂₀](OH)₄; talc; Mg₆[Si₈O₂₀](OH)₄; serpentine for example,asbestos; Kaolinite; Al₄[Si₄O₁₀](OH)₈; and vermiculite.

In addition, a surface treatment of the filler(s) may be performed, forexample with a fatty acid or a fatty acid ester such as a stearate, orwith organosilanes, organosiloxanes, or organosilazanes hexaalkyldisilazane or short chain siloxane diols to render the filler(s)hydrophobic and therefore easier to handle and obtain a homogeneousmixture with the other sealant components The surface treatment of thefillers makes the ground silicate minerals easily wetted by the siliconepolymer. These surface modified fillers do not clump, and can behomogeneously incorporated into the silicone polymer. This results inimproved room temperature mechanical properties of the uncuredcompositions. Furthermore, the surface treated fillers give a lowerconductivity than untreated or raw material. For the sake ofclarification it should be understood that fatty acids and/or fatty acidesters used for treating fillers are separate from those discussed as anessential additive of the present invention and typically anyhydrophobing treatment of the filler will have been done independentlyof the fatty acid and/or fatty acid esters essential to the presentinvention.

The proportion of such fillers when employed will depend on theproperties desired in the elastomer-forming composition and the curedelastomer. Usually the filler content of the composition will residewithin the range from about 5 to about 150 parts by weight per 100 partsby weight of the polymer excluding the extender portion.

Other ingredients which may be included in the compositions include butare not restricted to co-catalysts for accelerating the cure of thecomposition such as metal salts of carboxylic acids and amines;rheological modifiers; Adhesion promoters, pigments, Heat stabilizers,Flame retardants, UV stabilizers, cure modifiers Chain extenders,electrically and/or heat conductive fillers, Fungicides and/or biocidesand the like (which may suitably by present in an amount of from 0 to0.3% by weight), water scavengers, (typically the same compounds asthose used as cross-linkers or silazanes). It will be appreciated thatsome of the additives are included in more than one list of additives.Such additives would then have the ability to function in all thedifferent ways referred to.

The rheological additives include silicone organic co-polymers such asthose described in EP 0802233 based on polyols of polyethers orpolyesters; non-ionic surfactants selected from the group consisting ofpolyethylene glycol, polypropylene glycol, ethoxylated castor oil, oleicacid ethoxylate, alkylphenol ethoxylates, copolymers or ethylene oxide(EO) and propylene oxide (PO), and silicone polyether copolymers; aswell as silicone glycols. Some of these rheological additives mayadditionally enhance the adhesive properties of the composition.

Any suitable adhesion promoter(s) may be incorporated in a sealantcomposition in accordance with the present invention. These may includefor example alkoxy silanes such as aminoalkylalkoxy silanes,epoxyalkylalkoxy silanes, for example, 3-glycidoxypropyltrimethoxysilaneand, mercapto-alkylalkoxy silanes and γ-aminopropyl triethoxysilane,reaction products of ethylenediamine with silylacrylates. Isocyanuratescontaining silicon groups such as 1,3,5-tris(trialkoxysilylalkyl)isocyanurates may additionally be used. Further suitable adhesionpromoters are reaction products of epoxyalkylalkoxy silanes such as3-glycidoxypropyltrimethoxysilane with amino-substituted alkoxysilanessuch as 3-aminopropyltrimethoxysilane and optionally alkylalkoxy silanessuch as methyl-trimethoxysilane. epoxyalkylalkoxy silane,mercaptoalkylalkoxy silane, and derivatives thereof.

Heat stabilizers may include Iron oxides and carbon blacks, Ironcarboxylate salts, cerium hydrate, barium zirconate, cerium andzirconium octoates, and porphyrins.

Flame retardants may include for example, carbon black, hydratedaluminium hydroxide, and silicates such as wollastonite, platinum andplatinum compounds.

Chain extenders may include difunctional silanes which extend the lengthof the polysiloxane polymer chains before crosslinking occurs and,thereby, reduce the modulus of elongation of the cured elastomer. Chainextenders and cross-linkers compete in their reactions with thefunctional polymer ends; in order to achieve noticeable chain extension,the difunctional silane must have substantially higher reactivity thanthe typical trifunctional cross-linker. Suitable chain extenders forcondensation cure systems are, suitable chain extender include forexample:—

said chain extender being selected from the group of

-   (i) a Diacetamidosilane, a diacetoxysilane, a diaminosilane where    each amino group has one or two N—H bonds per nitrogen; a    dialkoxysilane, a diamidosilane, a hexaorganodisilazane, a    diketoximinosilane;-   (ii) a polydialkylsiloxane having a degree of polymerisation of from    2 to 25 and having at least two acetamido or acetoxy or amino or    alkoxy or amido or ketoximo substituents per molecule,-   (iii) an α-aminoalkyldialkoxyalkylsilane wherein the alkyl and    alkoxy groups contain from 1 to 6 carbon atoms,-   (iv) a compound of the structure ZMe₂SiO(Me₂SiO)_(y)SiMe₂Z or    ZMe₂Si—Y—SiMe₂Z    -   where Z is a heterocyclic Si—N group Y is a divalent hydrocarbon        radical selected from the group consisting of —(CR₂)_(m)— or        —C₆H₄—, y is 0 or a whole number, and m is 2 to 6 inclusive and        R is a monovalent hydrocarbon group;

Specific examples of chain extenders include alkenyl alkyldialkoxysilanes such as vinyl methyl dimethoxysilane, vinylethyldimethoxysilane, vinyl methyldiethoxysilane,vinylethyldiethoxysilane, alkenylalkyldioximosilanes such as vinylmethyl dioximosilane, vinyl ethyldioximosilane, vinylmethyldioximosilane, vinylethyldioximosilane,alkenylalkyldiacetoxysilanes such as vinyl methyl diacetoxysilane, vinylethyldiacetoxysilane, and alkenylalkyldihydroxysilanes such as vinylmethyl dihydroxysilane, vinyl ethyldihydroxysilane, vinylmethyldihydroxysilane,vinylethyldihydroxysilane.methylphenyl-dimethoxysilane, di-butoxydiacetoxysilane, Alkylalkenylbis(N-alkylacetamido) silanes such asmethylvinyldi-(N-methylacetamido)silane, andmethylvinyldi-(N-ethylacetamido)silane; dialkylbis(N-arylacetamido)silanes such as dimethyldi-(N-methylacetamido)silane; anddimethyldi-(N-ethylacetamido) silane; Alkylalkenylbis(N-arylacetamido)silanes such as methylvinyldi(N-phenylacetamido)silane anddialkylbis(N-arylacetamido) silanes such asdimethyldi-(N-phenylacetamido)silane, methylvinylbis(N-methylacetamido)silane, methylhydrogendiacetoxysilane,dimethylbis(N-diethylaminoxy) silane anddimethylbis(sec.-butylamino)silane. The chain extender used may alsocomprise any combination of two or more of the above.

Electrically conductive fillers may include carbon black, metalparticles such as silver particles any suitable, electrically conductivemetal oxide fillers such as titanium oxide powder whose surface has beentreated with tin and/or antimony, potassium titanate powder whosesurface has been treated with tin and/or antimony, tin oxide whosesurface has been treated with antimony, and zinc oxide whose surface hasbeen treated with aluminium.

Thermally conductive fillers may include metal particles such aspowders, flakes and colloidal silver, copper, nickel, platinum, goldaluminium and titanium, metal oxides, particularly aluminium oxide(Al₂O₃) and beryllium oxide (BeO); magnesium oxide, zinc oxide,zirconium oxide; Ceramic fillers such as tungsten monocarbide, siliconcarbide and aluminium nitride, boron nitride and diamond.

Any suitable Fungicides and biocides may be utilised, these includeN-substituted benzimidazole carbamate, benzimidazolylcarbamate such asmethyl 2-benzimidazolylcarbamate, ethyl 2-benzimidazolylcarbamate,isopropyl 2-benzimidazolylcarbamate, methylN-{2-[1-(N,N-dimethylcarbamoyl)benzimidazolyl]}carbamate, methylN-{2-[1-(N,N-dimethylcarbamoyl)-6-methylbenzimidazolyl]}carbamate,methylN-{2-[1-(N,N-dimethylcarbamoyl)-5-methylbenzimidazolyl]}carbamate,methyl N-{2-[1-(N-methylcarbamoyl)benzimidazolyl]}carbamate, methylN-{2-[1-(N-methylcarbamoyl)-6-methylbenzimidazolyl]}carbamate, methylN-{2-[1-(N-methylcarbamoyl)-5-methylbenzimidazolyl]}carbamate, ethylN-{2-[1-(N,N-dimethylcarbamoyl)benzimidazolyl]}carbamate, ethylN-{2-[2-(N-methylcarbamoyl)benzimidazolyl]}carbamate, ethylN-{2-[1-(N,N-dimethylcarbamoyl)-6-methylbenzimidazolyl]}carbamate, ethylN-{2-[1-(N-methylcarbamoyl)-6-methylbenzimidazolyl]}carbamate, isopropylN-{2-[1-(N,N-dimethylcarbamoyl)benzimidazolyl]}carbamate, isopropylN-{2-[1-(N-methylcarbamoyl)benzimidazolyl]}carbamate, methylN-{2-[1-(N-propylcarbamoyl)benzimidazolyl]}carbamate, methylN-{2-[1-(N-butylcarbamoyl)benzimidazolyl]}carbamate, methoxyethylN-{2-[1-(N-propylcarbamoyl)benzimidazolyl]}carbamate, methoxyethylN-{2-[1-(N-butylcarbamoyl)benzimidazolyl]}carbamate, ethoxyethylN-{2-[1-(N-propylcarbamoyl)benzimidazolyl]}carbamate, ethoxyethylN-{2-[1-(N-butylcarbamoyl)benzimidazolyl]}carbamate, methylN-{1-(N,N-dimethylcarbamoyloxy)benzimidazolyl]}carbamate, methylN-{2-[N-methylcarbamoyloxy)benzimidazolyl]}carbamate, methylN-{2-[1-(N-butylcarbamoyloxy)benzoimidazolyl]}carbamate, ethoxyethylN-{2-[1-(N-propylcarbamoyl)benzimidazolyl]}carbamate, ethoxyethylN-{2-[1-(N-butylcarbamoyloxy)benzoimidazolyl]}carbamate, methylN-{2-[1-(N,N-dimethylcarbamoyl)-6-chlorobenzimidazolyl]}carbamate, andmethyl N-{2-[1-(N,N-dimethylcarbamoyl)-6-nitrobenzimidazolyl]}carbamate.10,10′-oxybisphenoxarsine (trade name: Vinyzene, OBPA),di-iodomethyl-para-tolylsulfone,benzothiophene-2-cyclohexylcarboxamide-S,S-dioxide,N-(fluordichloridemethylthio)phthalimide (trade names: Fluor-Folper,Preventol A3). Methyl-benzimideazol-2-ylcarbamate (trade names:Carbendazim, Preventol BCM), Zinc-bis(2-pyridylthio-1-oxide) (zincpyrithion) 2-(4-thiazolyl)-benzimidazol, N-phenyl-iodpropargylcarbamate,N-octyl-4-isothiazolin-3-on,4,5-dichloride-2-n-octyl-4-isothiazolin-3-on,N-butyl-1,2-benzisothiazolin-3-on and/or Triazolyl-compounds, such astebuconazol in combination with zeolites containing silver.

The compositions are preferably room temperature vulcanisablecompositions in that they cure at room temperature without heating.

A composition in accordance with the present invention may be preparedby mixing the constituents of the composition employing any suitablemixing equipment. Optional constituents may be added as required. Forexample preferred one part, moisture curable compositions may be made bymixing together the diluted polymer having hydroxyl or hydrolysablegroups and filler used, and mixing this with a pre-mix of thecross-linker and catalyst. UV-stabilisers pigments and other additivesmay be added to the mixture at any desired stage. If required additionaldiluent may be blended with the other composition ingredients afterpolymerisation.

After mixing, the compositions may be stored under substantiallyanhydrous conditions, for example in sealed containers, until requiredfor use.

In accordance with the present invention there is provided a method toprepare a moisture curable composition capable of cure to an elastomericbody comprising

-   (a) preparing a diluted silicon containing polymer of the formula    X-A-X¹    where X and X¹ are independently selected from silyl groups which    contain one or more condensable substituents per group and A is a    polymeric chain having a number average molecular weight (M_(n)) of    at least 132 000; and a degree of polymerisation of at least 1800 by    polymerising a monomer and/or oligomer in the presence of an organic    based diluent material, a suitable catalyst and optionally an    end-blocker; and-   b) Where required quenching the polymerisation process; and then    blending the polymer with a suitable cross-linking agent which    comprises at least two groups which are reactable with the    condensable groups in the diluted polymer; a suitable condensation    catalyst and optionally one or more fillers.

The diluted silicon containing polymer is preferably anorganopolysiloxane containing polymer having hydroxyl and/orhydrolysable terminal end groups of the composition in accordance withthe present invention may be obtained by any suitable polymerisationprocess provided the polymer is diluted in the extender and/orplasticiser during the polymerisation process. Preferred routes to thepreparation of said diluted silicon containing polymer are by thefollowing routes

-   -   (i) polycondensation    -   (ii) ring opening/equilibrium    -   (iii) polyaddition    -   (iv) chain extension    -   (v)        wherein where required polymers resulting from the above        polymerisation routes may be end-capped to provide the required        hydrolysable end-groups.    -   (i) Polycondensation (i.e. the polymerisation of multiple        monomers and/or oligomers with the elimination of low molecular        weight by-product(s) such as water, ammonia or methanol etc).        Any suitable polycondensation reaction pathway may be utilised.        Preferred are polycondensation reactions relying on the reaction        schemes hereinbefore described for condensation reactions with        the interaction of compounds having hydroxyl and/or hydrolysable        end groups most preferred.

In the case where A is an organosiloxane chain, a preferred method forthe polymerisation process is the polymerisation of straight chainand/or branched organopolysiloxanes of formula (2) above in which R⁵ andsubscript s are as previously described The starting materials for thepolymerisation are preferably substantially linear materials, which areend-blocked with a siloxane group of the formula R″₃SiO_(1/2), whereineach R″ is the same or different and is R⁵ or a condensable group. Anysuitable combination of condensable end groups may be used for thepolymerisation process of the present invention (i.e. the condensablegroups chosen must be able to undergo a condensation reaction togetherin order to polymerise). Preferably at least one R″ group is a hydroxylor hydrolysable group. Typically the condensable groups used asmonomer/oligomer end-groups are silyl groups comprisinghydroxyl-terminating or hydrolysable substituents such as —SiOH₃,—(R^(a))SiOH₂, —(R^(a))₂SiOH, —R^(a)Si(OR^(b))₂, —Si(OR^(b))₃, —R^(a)₂SiOR^(b) or

—R^(a) ₂Si—R^(c)—SiR^(d) _(p)(OR^(b))_(3−p) where each R^(a), R^(b),R^(d), R^(c) and p are as hereinbefore described.

Starting materials for the condensation reaction of silanol containingsiloxanes are organopolysiloxane oligomers having silicon-bondedhydroxyl groups or hydrolysable groups such as alkoxy groups, which mayform silanol groups in situ. Preferably the starting materials have aviscosity of between 10 mPa·s and 5000 mPa·s. Some of the startingmaterials may comprise non-hydrolysable end-groups.

Many of the above processes require the presence of catalyst. Anysuitable polycondensation catalyst may be utilised. These include any ofthe catalysts described above for the condensation cure of thecomposition in accordance with the present invention, protic acids,Lewis acids, organic and inorganic bases, metal salts and organometalliccomplexes. Lewis acid catalysts. (a “Lewis acid” is any substance thatwill take up an electron pair to form a covalent bond). suitable for thepolymerisation in the present invention include, for example, borontrifluoride FeCl₃, AlCl₃, ZnCl₂, and ZnBr₂.

More preferred are condensation specific catalysts such as acidiccondensation catalysts of the formula R²⁰SO₃H in which R²⁰ represents analkyl group preferably having from 6 to 18 carbon atoms such as forexample a hexyl or dodecyl group, an aryl group such as a phenyl groupor an alkaryl group such as dinonyl- or didoecyl-naphthyl. Water mayoptionally be added. Preferably R²⁰ is an alkaryl group having an alkylgroup having from 6 to 18 carbon atoms such as dodecylbenzenesulphonicacid (DBSA). Other condensation specific catalysts include n-hexylamine,tetramethylguanidine, carboxylates of rubidium or caesium, hydroxides ofmagnesium, calcium or strontium and other catalysts as are mentioned inthe art, e.g. in GB patent specifications 895091, 918823 and EP 0382365.Also preferred are catalysts based on phosphonitrile chloride, forexample those prepared according to U.S. Pat. Nos. 3,839,388 and4,564,693 or EP application 215 470 and phosphonitrile halide ion basedcatalysts, as described in GB2252975, having the general formula [X³(PX³₂═N)_(s)PX³ ₃]⁺[M²X³ _((v−t+1))R^(III) _(t)]⁻, wherein X³ denotes ahalogen atom, M² is an element having an electronegativity of from 1.0to 2.0 according to Pauling's scale, R^(III) is an alkyl group having upto 12 carbon atoms, s has a value of from 1 to 6, v is the valence oroxidation state of M² and t has a value of from 0 to v−1.

Alternatively the catalyst may comprise an oxygen-containingchlorophosphazene containing organosilicon radicals having the followinggeneral formula:—Z¹—PCl₂═N(—PCl₂═N)_(n)—PCl₂—Oin whichZ¹ represents an organosilicon radical bonded to phosphorus via oxygen,a chlorine atom or the hydroxyl group andn represents 0 or an integer from 1 to 8. The catalyst may also comprisecondensation products of the above and/or tautomers thereof (thecatalyst exists in a tautomeric form when Z¹ is a hydroxyl group).

A further alternative catalyst which might be used as the catalyst inthe present invention is any suitable compound providing a source ofanions comprising at least one quadri-substituted boron atom and protonscapable of interaction with at least one silanol group as defined in WO01/79330.

The activity of the catalyst is preferably quenched by using aneutralizing agent which reacts with the catalyst to render itnon-active. Typically in the case of the acid type condensationcatalysts the neutralising agent is a suitable base such as an aminesuch as a mono/di and trialkanolamines for example monoethanolamine(MEA) and triethanolamine (TEA). In the case of systems using a DBSAcatalyst alternative quenching means include aluminasilicate zeolitematerials that were found to absorb DBSA and leave a stable polymer. Inmost cases catalyst residues remain in the polymer product or whereappropriate may be removed by filtration or alternative methods. In thecase of phosphazene based catalysts when the desired viscosity has beenreached, the viscosity of the organosilicon compound obtained in theprocess can be kept constant by a procedure in which the catalyst used,or a reaction product which has been formed from this catalyst byreaction with organosilicon compound to be subjected to condensationand/or equilibration and likewise promotes the condensation and/orequilibration of organosilicon compounds, is inhibited or deactivated byaddition of inhibitors or deactivators which have been employed to datein connection with phosphazenes, for example, triisononylamine,n-butyllithium, lithium siloxanolate, hexamethyldisilazane and magnesiumoxide.

Where appropriate any suitable end-blocking agent, which halts thepolymerization reaction and thereby limits the average molecular weight,may be used to introduce the silyl end groups described above as X² andX¹.

(II) Equilibration/Ring Opening

The starting material for equilibration polymerisation processes such asring-opening polymerisation is a cyclosiloxane (also known as a cyclicsiloxane). Cyclic siloxanes which are useful are well known andcommercially available materials. They have the general formula(R²¹SiO)_(m), wherein each R²¹ is R′ is as hereinbefore described and mdenotes an integer with a value of from 3 to 12. R²¹ can be substituted,e.g. by halogen such as fluorine or chlorine. The alkyl group can be,for example, methyl, ethyl, n-propyl, trifluoropropyl, n-butyl,sec-butyl, and tert-butyl. The alkenyl group can be, for example, vinyl,allyl, propenyl, and butenyl. The aryl and aralkyl groups can be, forexample, phenyl, tolyl, and benzoyl. The preferred groups are methyl,ethyl, phenyl, vinyl, and trifluoropropyl. Preferably at least 80% ofall R²¹ groups are methyl or phenyl groups, most preferably methyl.Preferably the average value of m is from 3 to 6. Examples of suitablecyclic siloxanes are octamethylcyclotetrasiloxane,hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane,cyclopenta(methylvinyl)siloxane, cyclotetra(phenylmethyl)siloxane,cyclopentamethylhydrosiloxane and mixtures thereof. One particularlysuitable commercially available material is a mixture of comprisingoctamethylcyclotetrasiloxane and decamethylcyclopentasiloxane. Typicallymoisture is present in the monomers. The water present acts as anend-blocker by forming OH end groups on the polymers.

Any suitable catalyst may be used. These include alkali metal hydroxidessuch as lithium hydroxide, sodium hydroxide, potassium hydroxide orcaesium hydroxide, alkali metal alkoxides or complexes of alkali metalhydroxides and an alcohol, alkali metal silanolates such as potassiumsilanolate caesium silanolate, sodium silanolate and lithium silanolateor trimethylpotassium silanolate. Other catalysts which might beutilised include the catalyst derived by the reaction of a tetra-alkylammonium hydroxide and a siloxane tetramer and the boron based catalystsas hereinbefore described.

Catalysts which are most preferred for the equilibrium type of reactionhowever are phosphonitrile halides, phosphazene acids and phosphazenebases as hereinbefore described.

Where required the polymer obtained may be end-blocked as a means ofregulating the molecular weight of the polymer and/or to addfunctionality. Suitable end-blocking agents include silanes having 1group capable of reacting with the terminal groups of the resultingpolymeric constituent prepared in the diluted polymer. Preferred silaneswhich may be utilised as end-blockers however for the purpose of thepresent invention. They are used to introduce the hydroxyl andhydrolysable groups depicted above as X² and X¹.

(III) Polyaddition

For the sake of this specification a “polyaddition” or “additionpolymerisation” process is a polymerisation process whereby unlike in acondensation reaction no by-products such as water or alcohols aregenerated from the monomeric and oligomeric co-reactants duringpolymerisation. A preferred addition polymerisation route is ahydrosilylation reaction between an unsaturated organic group e.g. analkenyl or alkynyl group and an Si—H group in the presence of a suitablecatalyst.

Typically the polyaddition route is utilised to form block copolymers byreacting

-   -   (a) (i) an organopolysiloxane or        -   (ii) silane with:—    -   (b) (i) one or more organopolysiloxane polymer(s) or        -   (ii) one or more organic polymer(s)        -   via an addition reaction pathway in the presence of the            extender and/or plasticiser, and a suitable catalyst and            optionally an end-blocking agent; and            where required quenching the polymerisation process.

The organopolysiloxane or silane (a) is selected from a silane (a) (ii)containing at least one group capable of undergoing addition typereactions and an organopolysiloxane monomer (a) (i) containing groupscapable of undergoing addition type reactions. The organopolysiloxane orsilane (a) must contain substituents such that it is capable ofundergoing an appropriate addition reaction with polymers (b) (i) or(ii). The preferred addition reaction is a hydrosilylation reactionbetween an unsaturated group and an Si—H group.

Preferably silane (a) (ii) has at least 1 and preferably 2 groupscapable of undergoing addition type reactions with (b) (i) or (ii). Whenthe addition reaction is a hydrosilylation reaction the silane maycontain an unsaturated constituent but preferably contains at least oneSi—H group. Most preferably each silane contains one or more Si—Hgroups. In addition to the one or more Si—H groups, preferred silanesmay include for example an alkyl group, an alkoxy group, an acyloxygroup, a ketoximato group, an amino group, an amido group, an acid amidogroup, an aminoxy group, a mercapto group, an alkenyloxy group and thelike. Among these, alkoxy, acyloxy, ketoximato, amino, amido, aminoxy,mercapto and alkenyloxy groups are preferred. Practical examples of thesilicon hydride are halosilane tri-chlorosilane, methyl dichlorosilane,dimethyl chlorosilane, and phenyl dichlorosilane; alkoxy silanes, suchas tri-methyoxy silane, tri-ethoxy silane, methyl di-ethoxy silane,methyl di-methoxy silane and phenyl-di-methoxy silane; acyloxy silanes,such as methyl di-acetoxy silane and phenyl diacetoxy silane; andketoximato silanes, such as bis-(dimethyl-ketoximate)-methyl silane andbis-(cyclohexyl ketoximate)methyl silane. Among them, halosilanes andalkoxyl silanes are preferred. Particularly preferred silanes includefor example methyl dimethoxy silane (H—Si(—CH₃)(—OCH₃)₂).

It will be appreciated that the addition reaction between silane (a)(ii) and (b) (i) or (ii) results in a polymer chain extension process oras a means of end—blocking a polymer with pre-required end groups, inwhich case the extender may be added in combination with silane (a)(ii), i.e. immediately prior to the addition reaction or may be presentduring the polymerisation of polymer (b) (i) and/or (b) (ii) and as suchsilane (a) (ii) is added to an extended polymer (b) (i) or (b) (ii)which has been polymerised in the presence of the extender.

Organopolysiloxane monomer (a) (i) is preferably in the form of astraight chain and/or branched organopolysiloxane of formula (1a)R′_(a)SiO_(4−a/2)  (1a)wherein each R′ may be the same or different and denotes a hydrocarbongroup having from 1 to 18 carbon atoms, a substituted hydrocarbon grouphaving from 1 to 18 carbon atoms or a hydrocarbonoxy group having up to18 carbon atoms and a has, on average, a value of from 1 to 3,preferably 1.8 to 2.2. Preferably each R′ is the same or different andare exemplified by, but not limited to hydrogen, alkyl groups such asmethyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, undecyl, andoctadecyl; cycloalkyl such as cyclohexyl; aryl such as phenyl, tolyl,xylyl, benzyl, and 2-phenylethyl; and halogenated hydrocarbon groupssuch as 3,3,3-trifluoropropyl, 3-chloropropyl, and dichlorophenyl. SomeR′ groups may be hydrogen groups. Preferably the polydiorganosiloxanesare polydialkylsiloxanes, most preferably polydimethylsiloxanes. Whenthe organopolysiloxane or silane (a) is an Organopolysiloxane monomer,said organopolysiloxane monomer must have at least one group which isreactable with at least two groups, typically the terminal groups, of(b) (i) or (ii) via an addition reaction process. Preferablyorganopolysiloxane (a) (i) comprises at least one Si—H per molecule,preferably at least two Si—H groups per molecule. Preferablyorganopolysiloxane (a) (i) is end-blocked with a siloxane group of theformula H(R″)₂SiO_(1/2), wherein each R″ is a hydrocarbon or substitutedhydrocarbon group, most preferably an alkyl group. Preferablyorganopolysiloxane (a) (i) has a viscosity of between 10 mPa·s and 5000mPa·s at 25° C.

Organopolysiloxane polymer (b) (i) is preferably a straight chain and/orbranched organopolysiloxane of formula (1b)R′″_(a)SiO_(4−a/2)  (1b)wherein each R′″ may be the same or different and denotes a hydrocarbongroup having from 1 to 18 carbon atoms, a substituted hydrocarbon grouphaving from 1 to 18 carbon atoms or a hydrocarbonoxy group having up to18 carbon atoms and a has, on average, a value of from 1 to 3,preferably 1.8 to 2.2. Preferably no R′″ groups may be hydrogen groups.Preferably each R′″ is the same or different and are exemplified by, butnot limited to alkyl groups such as methyl, ethyl, propyl, butyl,pentyl, hexyl, heptyl, octyl, undecyl, and octadecyl; cycloalkyl such ascyclohexyl; aryl such as phenyl, tolyl, xylyl, benzyl, and2-phenylethyl; and halogenated hydrocarbon groups such as3,3,3-trifluoropropyl, 3-chloropropyl, and dichlorophenyl.

Organopolysiloxane polymer (b) (i) may comprise any suitableorganopolysiloxane polymeric backbone but is preferably linear orbranched, and comprises at least one, preferably at least twosubstituent groups which will react with the aforementioned groups inthe organopolysiloxane or silane (a) via an addition reaction pathway.Preferably the or each substituent group of polymer (b) (i) is aterminal group. When the organopolysiloxane or silane (a) comprises atleast one Si—H group, the preferred substituent groups onorganopolysiloxane polymer (b) (i), which are designed to interact withthe Si—H groups, are preferably unsaturated groups (e.g. alkenylterminated e.g. ethenyl terminated, propenyl terminated, allylterminated (CH₂═CHCH₂—)) or terminated with acrylic or alkylacrylic suchas CH₂═C(CH₃)—CH₂— groups Representative, non-limiting examples of thealkenyl groups are shown by the following structures; H₂C═CH—,H₂C═CHCH₂—, H₂C═C(CH₃)CH₂—, H₂C═CHCH₂CH₂—, H₂C═CHCH₂CH₂CH₂—, andH₂C═CHCH₂CH₂CH₂CH₂—. Representative, non-limiting examples of alkynylgroups are shown by the following structures; HC≡C—, HC≡CCH₂—,HC≡CC(CH₃)—, HC≡CC(CH₃)₂—, HC≡CC(CH₃)₂CH₂— Alternatively, theunsaturated organic group can be an organofunctional hydrocarbon such asan acrylate, methacrylate and the like such as alkenyl an/or alkynylgroups. Alkenyl groups are particularly preferred.

The organic polymer (b) (ii) may comprise any suitable organic basedpolymer backbone for example the organic polymer backbone may comprise,for example, polystyrene and/or substituted polystyrenes such aspoly(α-methylstyrene), poly(vinylmethylstyrene),poly(p-trimethylsilylstyrene) andpoly(p-trimethylsilyl-α-methylstyrene). In each case the monomers usedfor organic polymer (b) (ii) comprise at least two substituent groups asdescribed for b(i) which will react with the reactive groups of theorganopolysiloxane or silane (a). Typically the organic polymer (b) (ii)comprises at least two unsaturated terminal groups, preferably alkenylterminal groups available for interaction with e.g. Si—H groups of theorganopolysiloxane or silane (a). Other organic based monomers (b) (ii)may include acetylene terminated oligophenylenes, vinylbenzyl terminatedaromatic polysulphones oligomers. Further organic polymeric backbonessuitable as (b) (ii) include aromatic polyester based monomers andaromatic polyester based monomers, both preferably comprising alkenylterminal groups.

Perhaps the most preferred organic based polymeric backbone for use aspolymer (b) (ii) are polyoxyalkylene based polymers (as hereinbeforedescribed) having unsaturated (e.g. alkenyl) terminal groups. The numberaverage molecular weight of each polyoxyalkylene polymer (b) may rangefrom about 300 to about 10,000. Moreover, the oxyalkylene units are notnecessarily identical throughout the polyoxyalkylene monomer, but candiffer from unit to unit.

Any appropriate method of making polyoxyalkylene monomers for use aspolymer (b) (ii) in the present application may be utilised. Examplesinclude those described in EP0397036, U.S. Pat. No. 3,971,751,EP0196565, and WO2005/103117. However, for the sake of this inventionthe method of preparation of the polyoxyalkylene polymer (b) isimmaterial with respect to the present invention. Any appropriate methodof making polyoxyalkylene amide polymers (b) discussed above may beutilised. Preferred methods include those described in WO9906473,WO200306530 and WO2005103117, the contents of which are incorporatedherein by reference.

In cases where the organopolysiloxane or silane (a) comprises only oneaddition reactable group and (b) (i) or (ii) comprises two additionreactable groups which will react with the organopolysiloxane or silane(a), the resulting product will be an “ABA” type polymeric product.Whereas when both the organopolysiloxane or silane (a) comprises onlyone addition reactable group and (b) (i) or (ii) comprises two additionreactable groups which will react with the organopolysiloxane or silane(a) interaction between the two components would lead to (AB)n blockcopolymers in which the length of the polymer is largely determined bythe relative amounts of the two constituents.

Hence linear non-hydrolyzable (AB)n block copolymers in accordance withthe present invention of this invention can be prepared by catalyzedhydrosilylation of alkenyl terminated polyethers with SiH-terminateddialkylsiloxane fluids. The resulting copolymer being a combination ofpolyoxyalkylene blocks linked through silicon to carbon to oxygenlinkages (i.e. a propyleneoxy group) and the endblocking groups beingselected from the group consisting of allyl, propenyl and/or hydrogen(dialkyl) siloxy groups (dependent on the relative amounts of theconstituents which are present).

When the addition reaction chosen is a hydrosilylation reaction, anysuitable hydrosilylation catalyst may be utilised. Such hydrosilylationcatalysts are illustrated by any metal-containing catalyst whichfacilitates the reaction of silicon-bonded hydrogen atoms of the SiHterminated organopolysiloxane with the unsaturated hydrocarbon group onthe polyoxyethylene. The metals are illustrated by ruthenium, rhodium,palladium, osmium, iridium, or platinum.

Hydrosilylation catalysts are illustrated by the following;chloroplatinic acid, alcohol modified chloroplatinic acids, olefincomplexes of chloroplatinic acid, complexes of chloroplatinic acid anddivinyltetramethyldisiloxane, fine platinum particles adsorbed on carboncarriers, platinum supported on metal oxide carriers such as Pt(Al₂O₃),platinum black, platinum acetylacetonate,platinum(divinyltetramethyldisiloxane), platinous halides exemplified byPtCl₂, PtCl₄, Pt(CN)₂, complexes of platinous halides with unsaturatedcompounds exemplified by ethylene, propylene, and organovinylsiloxanes,styrene hexamethyldiplatinum, Such noble metal catalysts are describedin U.S. Pat. No. 3,923,705, incorporated herein by reference to showplatinum based catalysts. One preferred platinum based catalyst isKarstedt's catalyst, which is described in Karstedt's U.S. Pat. Nos.3,715,334 and 3,814,730, incorporated herein by reference. Karstedt'scatalyst is a platinum divinyl tetramethyl disiloxane complex typicallycontaining one weight percent of platinum in a solvent such as toluene.Another preferred platinum based catalyst is a reaction product ofchloroplatinic acid and an organosilicon compound containing terminalaliphatic unsaturation. It is described in U.S. Pat. No. 3,419,593,incorporated herein by reference. Most preferred as the catalyst is aneutralized complex of platinous chloride and divinyl tetramethyldisiloxane, for example as described in U.S. Pat. No. 5,175,325.

Ruthenium catalysts such as RhCl₃(Bu₂S)₃ and ruthenium carbonylcompounds such as ruthenium 1,1,1-trifluoroacetylacetonate, rutheniumacetylacetonate and triruthinium dodecacarbonyl or a ruthenium1,3-ketoenolate may alternatively be used.

Other hydrosilylation catalysts suitable for use in the presentinvention include for example rhodium catalysts such as [Rh(O₂CCH₃)₂]₂,Rh(O₂CCH₃)₃, Rh₂(C₈H₁₅O₂)₄, Rh(C₅H₇O₂)₃, Rh(C₅H₇O₂)(CO)₂,Rh(CO)[Ph₃P](C₅H₇O₂), RhX⁴ ₃[(R³)₂S]₃, (R² ₃P)₂Rh(CO)X, (R² ₃P)₂Rh(CO)H,Rh₂X⁴ ₂Y² ₄, H_(a)Rh_(b)olefin_(c)Cl_(d), Rh (O(CO)R³)_(3−n)(OH)_(n)where X⁴ is hydrogen, chlorine, bromine or iodine, Y² is an alkyl group,such as methyl or ethyl, CO, C₈H₁₄ or 0.5 C₈H₁₂, R³ is an alkyl radical,cycloalkyl radical or aryl radical and R² is an alkyl radical an arylradical or an oxygen substituted radical, a is 0 or 1, b is 1 or 2, c isa whole number from 1 to 4 inclusive and d is 2, 3 or 4, n is 0 or 1.Any suitable iridium catalysts such as Ir(OOCCH₃)₃, Ir(C₅H₇O₂)₃,[Ir(Z)(En)₂]₂, or (Ir(Z²)(Dien)]₂, where Z² is chlorine, bromine,iodine, or alkoxy, En is an olefin and Dien is cyclooctadiene may alsobe used.

Additional components can be added to the hydrosilylation reaction whichare known to enhance such reactions. These components include salts suchas sodium acetate which have a buffering effect in combination withplatinum based catalysts.

The amount of hydrosilylation catalyst that is used is not narrowlylimited as long as there is a sufficient amount to accelerate a reactionbetween the polyoxyethylene having an unsaturated hydrocarbon group ateach molecular terminal and the SiH terminated organopolysiloxane atroom temperature or at temperatures above room temperature. The exactnecessary amount of this catalyst will depend on the particular catalystutilized and is not easily predictable. However, for platinum-containingcatalysts the amount can be as low as one weight part of platinum forevery one million weight parts of components the polyoxyethylene havingan unsaturated hydrocarbon group at each molecular terminal and the SiHterminated organopolysiloxane. The catalyst can be added at an amount 10to 120 weight parts per one million parts of components thepolyoxyethylene having an unsaturated organic group at each molecularterminal and the SiH terminated organopolysiloxane, but is typicallyadded in an amount from 10 to 60 weight parts per one million parts ofthe polyoxyethylene having an unsaturated organic group at eachmolecular terminal and the SiH terminated organopolysiloxane. Thepresent compositions can also be cured and/or crosslinked by ahydrosilylation reaction catalyst in combination with anorganohydrogensiloxane as the curing agent instead of an organicperoxide, providing each polymer molecule contains at least twounsaturated groups suitable for cross-linking with theorganohydrogensiloxane. These groups are typically alkenyl groups, mostpreferably vinyl groups. To effect curing of the present composition,the organohydrogensiloxane must contain more than two silicon bondedhydrogen atoms per molecule. The organohydrogensiloxane can contain, forexample, from about 4-20 silicon atoms per molecule, and have aviscosity of up to about 10 Pa·s at 25° C. The silicon-bonded organicgroups present in the organohydrogensiloxane can include substituted andunsubstituted alkyl groups of 1-4 carbon atoms that are otherwise freeof ethylenic or acetylenic unsaturation.

When the silicon containing material is a organopolysiloxane having atleast two Si—H groups, typically, the process is carried out usingapproximately a 1:1 molar ratio of Si—H containing polysiloxane and thematerial containing unsaturation. It is expected that useful materialsmay also be prepared by carrying out the process with an excess ofeither the Si—H containing polysiloxane or the material containingunsaturation, but this would be considered a less efficient use of thematerials. Typically, the material containing the unsaturation is usedin slight excess to ensure all the SiH is consumed in the reaction.

Where required the polymer obtained may be end-blocked as a means ofregulating the molecular weight of the polymer and/or to addfunctionality. Suitable end-blocking agents include silanes having 1group capable of undergoing addition type reactions with the terminalgroups in the diluted polymer. When the addition reaction is ahydrosilylation reaction the silane may contain an unsaturatedconstituent but preferably contains an Si—H group. In addition to theone or more Si—H groups, preferred silanes may include for example analkoxy group, an acyloxy group, a ketoximato group, an amino group, anamido group, an acid amido group, an aminoxy group, a mercapto group, analkenyloxy group and the like. Among these, alkoxy, acyloxy, ketoximato,amino, amido, aminoxy, mercapto and alkenyloxy groups are preferred.Practical examples of the silicon hydride are halosilanetri-chlorosilane, methyl dichlorosilane, dimethyl chlorosilane, andphenyl dichlorosilane; alkoxy silanes, such as tri-methyoxy silane,tri-ethoxy silane, methyl di-ethoxy silane, methyl di-methoxy silane andphenyl-di-methoxy silane; acyloxy silanes, such as methyl di-acetoxysilane and phenyl diacetoxy silane; and ketoximato silanes, such asbis-(dimethyl-ketoximate)-methyl silane and bis-(cyclohexylketoximate)methyl silane. Among them, halosilanes and alkoxyl silanesare preferred. Particularly preferred silanes include for example methyldimethoxy silane(H—Si(—CH₃)(—OCH₃)₂).

Hydrolysable groups which may be introduced using end-blockers and whererequired subsequent reactions include —SiOH₃, —(R^(a))SiOH₂,—(R^(a))₂SiOH, —R^(a)Si(OR^(b))₂, —Si(OR^(b))₃, —R^(a) ₂SiOR^(b) or—R^(a)Si—R^(c)—SiR^(d) _(p)(OR^(b))_(3−p) where each R^(a) independentlyrepresents a monovalent hydrocarbyl group, for example, an alkyl group,in particular having from 1 to 8 carbon atoms, (and is preferablymethyl); each R^(b) and R^(d) group is independently an alkyl or alkoxygroup in which the alkyl groups suitably have up to 6 carbon atoms;R^(c) is a divalent hydrocarbon group which may be interrupted by one ormore siloxane spacers having up to six silicon atoms; and p has thevalue 0, 1 or 2.

(IV) Chain Extension

In this case rather than adding chain extender into a final pre-preparedpolymer composition the extender is mixed into the polymer during achain extension polymerisation step prior to the introduction of theother constituents of the sealant composition. Typically the polymericstarting material is an organopolysiloxane having end groups suitablefor interaction with the chosen chain extending materials. Typically thepolymer end groups are either hydrolysable or suitable for additionreaction (typically hydrosilylation) and the chain extending material ischosen on the basis of having suitable reactive groups which will chainextend the polymer. Preferred chain extending materials for chainextending polymers having hydroxyl and/or hydrolysable end groups are ashereinbefore described.

For pre-formed polymers with alkenyl or Si—H end groups suitable foraddition reactions via a hydrosilylation route chain extender includefor example:—

For pre-formed polymers with alkenyl or Si—H end groups suitable foraddition reactions via a hydrosilylation route chain extender includefor example:—

A silane comprising two alkenyl groups, a dihydrosilane, apolydialkylsiloxane having a degree of polymerisation of from 2 to 25and at least one Si-alkenyl bond per terminal group,

A polydialkylsiloxane having a degree of polymerisation of from 2 to 25and at least one Si—H bond per terminal group and wherein each alkylgroup independently comprises from 1 to 6 carbon atoms;

organosilicon compounds with the general formula

in which R is as hereinbefore described, j is 1, 2, or 3, k is 0 or 1,and j+k is 2 or 3. exemplified by compounds with the following formulas,(ViMe₂SiO)₂SiVi(OMe)₁ (ViMe₂SiO)₁SiVi(OMe)₂, (ViMe₂SiO)₂SiVi(OEt)₁,(ViMe₂SiO)₁SiVi(OEt)₂, (ViMe₂SiO)₃Si(OMe)₁, (ViMe₂SiO)₂Si(OMe)₂,(ViMe₂SiO)₃Si(OEt)₁ and (ViMe₂SiO)₂Si(OEt)₂ As used herein, Virepresents a vinyl group, Me represents a methyl group, and Etrepresents an ethyl group.

The catalyst used to catalyse the chain extension reaction is determinedby the reaction to take place. When the reaction occurring is acondensation reaction any suitable condensation catalyst as hereinbeforedescribed may be utilised. When the reaction occurring is ahydrosilylation reaction any suitable hydrosilylation catalyst ashereinbefore described may be utilised.

Where required the polymer contains hydrolysable terminal groups,end-blocking agents as described above in relation to condensation maybe utilised to obtain appropriate terminal groups. Where required thepolymer contains addition reactable terminal groups, end-blocking agentsas described above in relation to polyaddition may be utilised to obtainappropriate terminal groups.

The process can be carried out either batchwise or continuously on anysuitable mixers. In case of a polycondensation, generated water caneither be removed by chemical drying using e.g. hydrolysable silaneslike methyltrimethoxysilane or by physical separation using evaporation,coalescing or centrifuging techniques.

Chain extension may take place at any suitable temperature and pressurefor the process concerned in batch or continuous modes of operation aspreferred. Hence in the case of the phosphazene catalysed methodspolymerisation may occur at temperatures of between 50° C. to 200° C.,more preferably 80° C. to 160° C. Furthermore, in order to facilitateremoval of the by-products formed during the condensation, for example,water, HCl or alcohol, the condensation and/or equilibration of theorganosilicon compounds may be carried out at a pressure below 80 kPa.Alternative methods for the removal of condensation by-products includeremoval by chemical drying using e.g. hydrolysable silanes likemethyltrimethoxysilane (where appropriate) or by physical separationusing evaporation, coalescing or centrifuging techniques.

The process can be carried out either batchwise or continuously on anysuitable mixers. In case of a polycondensation, generated water caneither be removed by chemical drying using e.g. hydrolysable silaneslike methyltrimethoxysilane or by physical separation using evaporation,coalescing or centrifuging techniques.

The invention will now be described by way of Example. For the sake ofcomparison the extender used in all the examples and comparativeexamples unless otherwise indicated was HYDROSEAL® G250H, a hydrotreatedmineral oil cut (n-para 7% iso-para 51% and naphthenic 42%) produced byTotal Fina. All viscosity values were measured at 25° C. unlessotherwise indicated.

EXAMPLE 1 Chain Extension Using a Dibutylacetoxysilane

Production of the Polymer

50 g of dimethylhydroxy terminated polydimethylsiloxane having aviscosity of 80,000 mPa·s at 25° C. was placed in a suitable container.0.2 g of dibutoxydiacetoxysilane (DBDAc) and 500 ppm weight (in relationto the polymer) of dibutyltindiacetate catalyst were added together witha stoichiometric quantity of water to hydrolyze the acetoxy groups onthe DBDAc. As soon as an initial viscosity increase in viscosity wasdetected 50 g of extender were introduced into the reaction mixture andthe variation in viscosity was tracked until the viscosity of theproduct reached a maximum.

Sealant Formulation

The resulting polymer sealant (sample 1) was formulated with 86.485%weight polymer produced as described above, 5% weight of a 50% mixtureof methyl triacetoxysilane and ethyl triacetoxysilane cross-linker, 8%weight of fumed silica, 0.5% weight of Poly (PO)(EO) (rheology modifier)and 0.015% of dibutyltindiacetate catalyst. The sealant properties areshown in Table 1.

Adhesion test (7dRT) was carried out to show that a bead of sealantsuccessfully bonded to a standard glass plate after being allowed tocure at 23° C. and 50% relative humidity for 7 days. Adhesion wasassessed by subsequent to the curing period the beads were pulled at 90°and the failure was rated as follows:

0: adhesive failure—poor adhesion)

1: boundary or mixed mode (adhesive/cohesive) failure—acceptableadhesion.

2: cohesive failure—excellent adhesion

Adhesion test (7H₂O) was carried out to show that a bead of sealantsuccessfully bonded to a standard glass plate after being allowed tocure at 23° C. and 50% relative humidity for 7 days and thensubsequently 7 days in water. The bead of sealant was pulled as inadhesion test (7dRT).

The cure in depth tests were undertaken to determine how far below thesurface the sealant had hardened in 24 and 72 hours by filling asuitable container (avoiding the introduction of air pockets) withsealant, curing the sealant contained in the container for theappropriate period of time at room temperature (about 23° C.) and about50% relative humidity. After the appropriate curing time the sample isremoved from the container and the height of the cured sample ismeasured.

TABLE 1 Standards properties Test method Sample 1 Tack Free Time (min)ASTM D2377-94 24 Penetration (mm/10 * 3 sec) ASTM D217-97 170 Cure indepth 24 h 1.5 (mm/24 h) Cure in depth 72 h 1.7 (mm/72 h) Specifygravity (kg/l) ASTM D1475-98 0.94 Tensile Strength ASTM D412-98a 0.6(sheet 2 mm) (MPa) Elongation at break (%) ASTM D412-98a 1047 100%modulus (MPa) ASTM D638-97 0.13 Hardness (Shore A) ASTM D2240-97 5Adhesion Tests 7dRT 7H₂O glass 2 2

EXAMPLE 2

The polymer was produced in a laboratory batch reactor having a mixingpaddle which mixes a mixture at the same rate (in the following example179 revolutions per minute (RPM) continuously by varying the power inline with the change in viscosity and thereby using the followingprocedure:

0.42 kg of dimethylhydroxy terminated polydimethylsiloxane (70 mPa·s)and was introduced into the mixer and stirred sequentially adding 21 gof DBSA catalyst and 0.56 kg of diluent while continuing stirring at 179RPM. The viscosity of the resulting polymer was tracked by measuring thecurrent (mA) required to maintaining the paddle rotation speed of 179RPM. Mixing was continued until the viscosity began to drop at whichpoint the catalyst was neutralised with an amine (e.g. 0.5-1.0%triethanolamine). The number averaged molecular weight of the dilutedpolydimethylsiloxane polymer prepared was 170,000. determined usingASTMD5296-05 on the basis of polystyrene molecular weight equivalents.Table 2 shows the formulation of the polymer.

TABLE 2 Sample 2 Diluted Polymer Viscosity (mPa · s) at 25° C. 19,000 Wt% organopolysiloxane 39.3 Wt % Diluent 58.9 Wt % DBSA 1.5 Wt %Monoethanolamine 0.3

The resulting diluted organopolysiloxane polymer was used as the polymercomponent in an acetoxy sealant formulation prepared by mixing thediluted polymer as prepared above with the other ingredients of thecomposition. The physical properties of the resulting sealant (Sample 2)were compared with those of a traditionally produced extended acetoxysealant formulation having a viscosity of 80 000 mPa·s at 25° C.(Comp. 1) using a polymer polymerized in the absence of diluentmaterial. Table 2 shows the formulation of the acetoxy sealant produced.

TABLE 3 Sample 2 Comp. 1 Total Wt % Extended Polymer 86.385 — Wt %organopolysiloxane (blended with diluent — 56.385 subsequent topolymerization Wt % Diluent (blended with polymer) — 30 Wt %triacetoxysilane 5 5 Wt % Fumed Silica (surface area 150 m²/g 8.6 8.6(BET)) Dibutyltin acetate 0.015 0.015Physical Properties of Sealant

Standard physical property tests were undertaken to compare theproperties of the two sealant formulations after curing (Table 4). TheAdhesion testing was undertaken as hereinbefore described in Example 1.

TABLE 4 Test Method Sample 1 Comp. 1 Specific Gravity ASTM D1475-98 0.900.97 Extrusion Rate (g/min) ASTM D2452-94 594 700 Tensile Strength (Mpa)ASTM D412-98a 1.16 2.08 Elongation at Break (%) ASTM D412-98a 1098 480Modulus 100% (Mpa) ASTM D638-97 0.13 0.44 Hardness (Shore A) ASTMD2240-97 2.00 13 Adhesion on glass (1) 2 (PASS) 2 (PASS) Adhesion onglass (2) 2 (PASS) 2 (PASS)

It will be appreciated that the acetoxy sealant made in accordance withthe present invention has a number of advantages over the prior artformulation, for example there is a higher diluent content for a similarrheology (50% vs 30%). The mixing process during the preparation of thesealant is significantly simplified because no blending step forblending polymer and diluent is required. The resulting sealant shows anincrease in elasticity as can be seen from the elongation at break ofgreater than 1000%. This sealant formulation enables the use of polymerswhich would have had substantially unworkable viscosities were it notfor the presence of the diluent during the polymerisation process e.g. 3400 000 mPa·s without any significant handling difficulties and the factthat the resulting uncured sealant composition has a significantly lowerspecific gravity enables the manufacturer to fill more sealantcartridges or other packages per kg of sealant produced.

EXAMPLE 3

Two acetoxy sealant formulations (samples 3 and 4) were prepared using apolymer prepared in accordance with the present invention and thephysical properties were compared with those of a traditionally producedextended acetoxy sealant formulation having a viscosity of 80 000(mPa·s) (comp. 2).

Diluted Polymer Samples 3 and 4 were prepared through polymerization ofcyclic organopolysiloxanes having the formula ((CH₃)₂SiO)₄ with aphosphazine base catalyst in the presence of Isopar® P hydrocarbon fluid(sold by Exxonmobil Corporation) as extender which has a initial boilingpoint of 235° C. and final boiling point of 265° C. (ASTM D 86) and aviscosity of 3.0 mPa·s. (ASTM D 445). The hydroxy terminatedpolydimethylsiloxane was used as the end-blocker and the silyl phosphatewas the selected neutralising agent. The polymer formulations are shownin Table 5

TABLE 5 EXTENDED POLYMER FORMULATION Sample 3 Sample 4 Polymerisationtemperature 100° C. 120° C. ((CH₃)₂SiO)₄ (wt %) 78.394 59.795 hydroxyterminated polydimethylsiloxane 1.60 0.20 70 mPa.s at 25° C. (wt %)Extender (wt %) 20 40 phosphazene base catalyst (wt %) 0.0035 0.0028Silyl phosphate (wt %) 0.0025 0.0022

Table 6 shows the residual monomer left in the composition aftercompletion of the polymerisation reaction together with details of themolecular weight of the polymer obtained for both sample 3 and sample 4(ASTM D5296-05). The residual monomer may be stripped out of the polymerif required as the boiling point thereof is significantly lower thanthat of the diluent. The boiling point of ((CH₃)₂SiO)₄ is 175° C.

TABLE 6 Sample 1 Sample 2 residual ((CH₃)₂SiO)₄ (wt %) 7.3 11.3 Numberaveraged molecular weight (Mn) 195,335 255,394 Weight averaged molecularweight (Mw) 429,789 561,100

An organopolysiloxane sealant composition was prepared from theresulting extended polymers described in Table 3 above. Samples 3 and 4in Table 7 were prepared from polymer Samples 3 and 4 in table 6respectively. In this case an additional amount of extender was added tothe extended polymer to further reduce the viscosity. The sealantformulations both for the sealant prepared according to the inventionand the comparative example. The details of the compositions wereprovided in Table 7

TABLE 7 Sample 3 Sample 4 Comp 2 Total Wt % Extended Polymer 43.2 43.3 —hydroxy terminated organopolysiloxane — — 56.4 80 000 mPa · s at 25° C.(wt %) (blended with diluent after to polymerisation) Diluent (blendedwith polymer 43.2 43.3 30 subsequent to polymerisation) (wt %)Triacetoxysilane (wt %) 5 5 5 Fumed Silica (surface area 150 m²/g 8.5858.585 8.585 (BET)) (wt %) Dibutyltin acetate (wt %) 0.015 0.015 0.015Physical Properties of Sealant

Standard physical property tests were in accordance with example 1 aboveunless otherwise indicated and the results are provided in Table 8.

TABLE 8 PHYSICAL PROPERTIES OF SEALANT Test Method Sample 3 Sample 4Comp 2 Specific Gravity ASTM D1475-98 0.92 0.90 0.97 Penetration ASTMD217-97 152 180 300 (mm/10) Tensile Strength ASTM D412-98a 4.34 4.982.08 (Mpa) Elongation at ASTM D412-98a >1000 >1000 480 Break (%) Modulus100% ASTM D638-97 0.12 0.09 0.44 (Mpa) Shore A Hardness ASTM D2240-97 41 13 Adhesion on glass 2 (PASS) 2 (PASS) 2 (PASS) (7H₂O) Adhesion onglass 2 (PASS) 2 (PASS) 2 (PASS) (7dRT)

It will be appreciated that the acetoxy sealant made in accordance withthe present invention has a number of advantages over the prior artformulation, The resulting sealant shows an increase in elasticity ascan be seen from the elongation at break of greater than 1000%. Thissealant formulation enables the use of polymers which would have hadsubstantially unworkable viscosities were it not for the presence of thediluent during the polymerisation process without any significanthandling difficulties and the fact that the resulting uncured sealantcomposition has a significantly lower specific gravity enables themanufacturer to fill more sealant cartridges or other packages per kg ofsealant produced.

1. A moisture curable composition capable of cure to an elastomeric bodycomprising (a) a diluted polymer comprising (i) a silicon containingpolymer of the formulaX-A-X¹ where X and X¹ are independently selected from silyl groups whichcontain one or more condensable substituents per group and A is apolymeric chain having a number average molecular weight (M_(n)) of atleast 132,000, and (ii) an organic extender and/or plasticiser whichdiluted polymer is obtained by polymerisation in the presence of theorganic extender and/or plasticiser (b) a suitable cross-linking agentwhich comprises at least two groups which are reactable with thecondensable groups in the diluted polymer, (c) a suitable condensationcatalyst, and optionally (e) one or more fillers.
 2. A composition inaccordance with claim 1 wherein A is a siloxane polymeric chain, anorganic polymeric chain, a siloxane copolymeric chain or asiloxane/organic block copolymeric chain.
 3. A composition in accordancewith claim 1 wherein X¹ or X are silyl groups comprisinghydroxyl-terminating or hydrolysable substituents selected from—Si(OH)₃, —(R^(a))Si(OH)₂, —(R^(a))₂SiOH, —R^(a)Si(OR^(b))₂,—Si(OR^(b))₃, —R^(a) ₂SiOR^(b) or —R^(a) ₂Si—R^(c)—SiR^(d)_(p)(OR^(b))_(3−p) where each R^(a) independently represents an alkylgroup; each R^(b) and R^(d) group is independently an alkyl or alkoxygroup in which the alkyl groups suitably have up to 6 carbon atoms;R^(c) is a divalent hydrocarbon group which may be interrupted by one ormore siloxane spacers having up to 6 silicon atoms; and p has the value0, 1 or
 2. 4. A composition in accordance with claim 1 wherein theextender and/or plasticiser is selected from one or more of the groupof: trialkylsilyl terminated polydimethyl siloxane, polyisobutylenes(PIB), phosphate esters, polyalkylbenzenes, and linear and/or branchedalkylbenzenes esters of aliphatic monocarboxylic acids.
 5. A compositionin accordance with claim 1 wherein the extender is selected from one ormore of the group comprising: linear or branched mono unsaturatedhydrocarbons; and mineral oil fractions comprising linear (n-paraffinic)mineral oils, branched (iso-paraffinic) mineral oils, cyclic(naphthenic) mineral oils, and mixtures thereof.
 6. A composition inaccordance with claim 1 wherein the cross-linking agent is one or moresilane or siloxane which contain acyloxy groups and/or ketoximino groupsand the catalyst is a tin catalyst.
 7. A composition in accordance withclaim 1 wherein the cross-linking agent is one or more silane orsiloxane which contain alkoxy groups and alkenyloxy groups and thecatalyst is a titanate or zirconate or a chelated titanate or chelatedzirconate.
 8. A composition in accordance with claim 1 wherein thefiller is present and comprises one or more finely divided, reinforcingfillers selected from the group of high surface area fumed silica,precipitated silica, and calcium carbonate, and/or one or more extendingfillers selected from the group of crushed quartz, diatomaceous earth,barium sulphate, iron oxide, titanium dioxide, carbon black, talc, andwollastonite.
 9. A composition in accordance with claim 1 wherein thediluted polymer is obtained by polymerisation in the extender and/orplasticiser via one of the following pathways: (i) condensation; (ii)ring opening/equilibrium; (iii) polyaddition; and (iv) chain extensionwherein where required polymers resulting from the above polymerisationroutes may be end-capped to provide the required hydrolysableend-groups.
 10. Joint sealants, adhesives, moulded bodies, coatings andformed-in-place gaskets comprising the composition in accordance withclaim
 1. 11. A sealant composition comprising the composition ofclaim
 1. 12. A method of sealing a space between two units, said methodcomprising applying a composition in accordance with claim 1 and causingor allowing the composition to cure.
 13. A composition in accordancewith claim 2 wherein the (i) silicon containing polymer has a viscosityof greater than 1,000,000 mPa·s at 25° C.
 14. A composition inaccordance with claim 3 wherein the (i) silicon containing polymer has aviscosity of greater than 1,000,000 mPa·s at 25° C.
 15. A composition inaccordance with claim 6 wherein the (i) silicon containing polymer has aviscosity of greater than 1,000,000 mPa·s at 25° C.
 16. A composition inaccordance with claim 7 wherein the (i) silicon containing polymer has aviscosity of greater than 1,000,000 mPa·s at 25° C.
 17. A composition inaccordance with claim 9 wherein the (i) silicon containing polymer has aviscosity of greater than 1,000,000 mPa·s at 25° C.
 18. A moisturecurable composition capable of cure to an elastomeric body comprising:(a) a diluted polymer comprising; (i) a silicon containing polymer ofthe formulaX-A-X¹ where X and X1 are independently selected from silyl groups whichcontain one or more condensable substituents per group and A is asiloxane polymeric chain, an organic polymeric chain, a siloxanecopolymeric chain or a siloxane/organic block copolymeric chain having anumber average molecular weight (Mn) of at least 132,000, and whereinsaid silicon containing polymer has a viscosity of greater than1,000,000 mPa·s at 25° C., and (ii) an organic extender and/orplasticizer, which diluted polymer is obtained by polymerisation in thepresence of the organic extender and/or plasticizer, (b) a suitablecross-linking agent which comprises one or more silanes or siloxaneswhich contain acyloxy groups, ketoximino groups, alkoxy groups and/oralkenyloxy groups which are reactable with the condensable groups in thediluted polymer, (c) a condensation catalyst selected from the groupconsisting of tin, a titanate, a zirconate, a chelated titanate, and achelated zirconate, and optionally (e) one or more fillers.
 19. Acomposition in accordance with claim 18 wherein X¹ or X are silyl groupscomprising hydroxyl-terminating or hydrolysable substituents selectedfrom —Si(OH)₃, —(R^(a))Si(OH)₂, —(R^(a))₂SiOH, —R^(a)Si(OR^(b))₂,—Si(OR^(b))₃, —R^(a) ₂SiOR^(b) or —R^(a) ₂Si—R^(c)—SiR^(d)_(p)(OR^(b))_(3−p) where each R^(a) independently represents an alkylgroup; each R^(b) and R^(d) group is independently an alkyl or alkoxygroup in which the alkyl groups suitably have up to 6 carbon atoms;R^(c) is a divalent hydrocarbon group which may be interrupted by one ormore siloxane spacers having up to 6 silicon atoms; and p has the value0, 1 or
 2. 20. A moisture curable composition capable of cure to anelastomeric body comprising: (a) a diluted polymer comprising; (i) asilicon containing polymer of the formulaX-A-X¹ where X and X¹ are independently selected from silyl groups whichcontain one or more condensable substituents per group and A is apolymeric chain having a number average molecular weight (M_(n)) of atleast 132,000, and wherein said silicon containing polymer has aviscosity of greater than 1,000,000 mPa·s at 25° C., and (ii) an organicextender and/or plasticizer, which diluted polymer is obtained bypolymerisation in the presence of the organic extender and/orplasticizer, (b) a suitable cross-linking agent which comprises at leasttwo groups which are reactable with the condensable groups in thediluted polymer, (c) a suitable condensation catalyst, and optionally(e) one or more fillers.
 21. A composition in accordance with claim 1wherein A includes siloxane units of the formula: —(R⁵_(s)SiO_((4−s)/2)) wherein each R⁵ is independently an organic grouphaving from 1 to 18 carbon atoms, a substituted hydrocarbon group havingfrom 1 to 18 carbon atoms or a hydrocarbonoxy group having up to 18carbon atoms and s has a value of from 1 to 3.